Rename some BuildOptions to avoid D keywords.

Add support for a "mainSourceFile" field. ...

The main source file is used as the root to access the whole package. This is important for dependency based building, such as with RDMD and for special build kinds, such as for a future unit test command. This also improves the robustness of "dub build --rdmd".

Main source files are automatically inferred as follows, if not explicitly given:
 1. search first in "source/", followed by "src/"
 2. take the first match of ("app.d", "main.d", "<pkgname>/main.d", "<pkgname>/<pkgname.d>") as the main file for the automatic "application" configuration
 3. take the first match of ("<pkgname>/all.d", "<pkgname>/package.d", "<pkgname>/<pkgname>.d") as the main file for the automatic "library" configuration

Import and string import files are now added to generated VisualD projects and "dub describe".

Support excluding paths using glob matching.

Remove dub.internal.std.process compatibility code as it doesn't support browse() and the compile status on older DMD versions isn't tracked anyway.

Fix handling of lib flags on Windows for GDC/LDC.

Fix "-w" to be the default warnings mode again.

Let the individual compiler classes handle passing arguments to the compiler. Fixes #86.

Change BuildOptions.init from "debug_" to the new "none" to fix bogus -debug flags during compilation. ...

Also fix formatting and enable the warning about using --debug=xxx compiled flags directly.

Generalize common compiler switches in the form of a BuildOptions enum. ...

Related changes:
 - translation of DMD compiler switches to other compilers is generalized
 - application of build requirements is generalized
 - added support for debug versions
 - supporting almost all compiler settings for generated VisualD projects now

Improve adherence to code conventions.

Fix building of libraries with no explicit target type set. See #87.

Ignore import libraries when building a static library. Fixes #91.

Add "workingDirectory" build setting to change the working directory from which the final executable will be run. Fixes #84.

Avoid bogus warnings about non-recommended dflags.

Introduce TargetType.none, fix handling of non-target project's dependencies and avoid continuous reinstalls of referenced sub-packages.

Rename log levels to be in line with the latest vibe.d versions.

Compiler and linker flags are not added in a unique way anymore. ...

This was breaking command lines such as "--framework A --framework B" on Mac OS.

Avoid calling pkg-config with no libs present.

Deprecate "relaxProperties", remove the default -property switch and warn about using them. Fixes #73.

Implement the "noDefaultFlags" build requirement. Fixes #68.

Attempt to fix handling of "-Wl" flags returned by "pkg-config".

Move all source files outside of "dub" to "dub/internal".

Warn on more special compiler flags.

Implemented "buildRequirements" as a way to avoid certain compiler settings for specific code bases. ...

See also #61.

Improve output of the dflags warning message. Fixes #54.

Output warning if DUB controlled compiler flags are specified in package.json. Fixes #37.

TODO "optimize": Done ...

Suffix checking easier and more efficient.

I also fixed some unittests some others that triggered I disabled (Soenke please review).

Implemented experimental separate compile/link building (used for dmd).

Added "targetName" and "targetPath" build settings and some fixes. ...

Other changes:
 - Made the comparison for "excludedSourceFiles" path format agnostic
 - Fixed the output directory for the VisualD generator
 - Removed the "binaryPath" global setting (which was undocumented up to now)

See also #26 and #29.