Fix Windows binary releases

Use build.d everywhere and take arguments by parameter ...

It seems easier to forward arguments from the build script this way,
and it's much more common to change the build arguments than the version.

Merge pull request #1848 from Geod24/fix1474 ...

Add a warning / workaround for issue 1474
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Fix issue 1277: Missing dub.json causes infinite loop ...

For some reason, having a 'source/app.d' was recognized as being in a package.
This would load an empty package with no manifest and send the dependency resolver
in an infinite loop.
Remove the special detection of 'source/app.d' and rely only on manifest.
Another option would have been to detect 'source/app.d' as a single-file package,
but that is a bit too much magic (the user can just 'dub run --single source/app.d').

Add a warning / workaround for issue 1474

example/generated-sources: Quote shell arguments

Merge pull request #1833 from Geod24/scripts-replacement ...

Improve travis-ci.sh
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Merge pull request #1843 from MartinNowak/merge_stable ...

Merge remote-tracking branch 'upstream/stable' into merge_stable
merged-on-behalf-of: Mathias LANG <pro.mathias.lang@gmail.com>

Merge pull request #1821 from Geod24/build-script ...

Replace `build.sh` and `build.cmd` with `build.d`
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Merge remote-tracking branch 'upstream/stable' into merge_stable

Merge pull request #1842 from Geod24/changelog ...

Remove leftover and outdated CHANGELOG.md file

Merge pull request #1838 from Geod24/cleanup ...

Windows: Remove Roaming repository migration
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

update version to v1.19.0-rc.1

Remove traces of VibeCustomMain ...

VibeCustomMain support was removed in Vibe.d v0.7.0,
released over 4 years ago (2015-11-04).

Remove leftover and outdated CHANGELOG.md file ...

DUB switched to using fragments from the 'changelog' directory
in PR1455 (v1.10, 2018-07-04), but the CHANGELOG.md was left
in place with the assumption a script to maintain it would
be written.
However, no such script has been written, and there doesn't
need to be a need for one either.

Merge pull request #1841 from ShigekiKarita/fix-stdout-flush ...

add flush before reading input for Windows msys2/mingw
merged-on-behalf-of: Petar Kirov <PetarKirov@users.noreply.github.com>

remove version (Windows)

add flush before reading input

Windows: Remove Roaming repository migration ...

This feature has been implemented in Dub v1.8.0, almost 2 years ago.

Add a contributor note about backwards compatiblity (#1837)

Merge pull request #1834 from Geod24/shadowing ...

Remove foreach variable shadowing
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Remove foreach variable shadowing

travis-ci.sh: Re-organize blocks more logically ...

Put the 'regular' test code at the beginning,
and the part that relies on COVERAGE being defined only once at the end.
Those could eventually be split in the future.

travis-ci.sh: Remove always true if condition

Replace `build.sh` and `build.cmd` with `build.d` ...

Since dub needs a D compiler anyway, we might follow in DMD's step and use D for building,
as it is more reliable and expressive than a shell script as features pile up.

This unifies the two scripts to expose the same set of functionalities on all platforms,
with a behavior that is hopefully more sensible
(tradeoff and reasoning are explained through the code / documentation).
It is also completely independent from the current working directory.

Some discrepancies included:
- Name of the variable to override to select the compiler (DC vs DMD);
- Version file: Windows was always regenerating it;
- Version file: Windows would display "unknown" if `dub describe` failed,
  POSIX would use an empty string;
- Compiler detection: POSIX would detect ldmd2 / gdmd if dmd is not present,
  Windows would just fail;

All those functionalities are now unified in a single script.
The old script are kept for compatibility, but forward to the new script,
and can be removed in a few releases.

Merge pull request #1831 from MartinNowak/merge_stable ...

Merge remote-tracking branch 'upstream/stable' into merge_stable

Merge remote-tracking branch 'upstream/stable' into merge_stable

update version to v1.19.0-beta.1

Merge remote-tracking branch 'upstream/master' into stable

Fix local cache