Support :subpackage shorthand syntax. Fixes #315. ...

This works for dependencies, as well as for referencing sub packages on the command line.

Display the build date for "dub -h".

Add the --build-mode switch to control how the compiler and linker are invoked.

Merge pull request #306 from ColdenCullen/master ...

Allow System and Local flags on all commands

Added old --system and --local flags back, but marked as deprecated.

Switched to '--cache=x' param type for package fetching.

Add hint to run "dub <cmd> -h" when usage errors occur.

Removed 'Wide' from PlacementLocation member names.

Merge branch 'upstreammaster' ...

Conflicts:
	source/dub/project.d

Add spellchecker to dub for --config mismatches.

Removed logInfo from commandline.

Added support for fetching to any location, now need to add support for finding packages in other locations.

Implement a basic "clean" command. Fixes #134.

Switched dub.fetch() to take an enum FetchOptions instead of 4 bools.

Fix member naming convention.

Fix the --compiler help message to mark the correct default compiler. See #303.

Set default compiler to be the same that built dub

Add a --missing-only switch to "dub upgrade". Fixes #271.

Use URL and Path types of vibe.d if available for better interop.

Rename UpdateOptions->UpgradeOptions and move it to dub.dub.

Avoid exponential run time in the dependency resolution algorithm if possible. ...

When going through all combinations of package versions, all sub trees of the search space are now skipped for a conflicting node, as those are guaranteed to conflict anyway.

Disable log output during "dub describe" to ensure only JSON gets written. See #221. ...

Note that JSON will only get written when no errors occur. Otherwise the output will be the usual error messages.

Add command line interface for managing package overrides.

Refactor runDubCommandLine to use less indentation/nesting.

Only validate (and output warnings) the root package once.

Implement a new dependency resolution algorithm with support for selections. ...

The new algorithm is completely rewritten to be able to find any valid combination of dependencies/versions. The old one could error out in cases where a valid dependency tree could have been built. Now the current selections are also taken into account when invoking without UpdateOptions.upgrade.

Some side changes:
 - Comparing branch versions is allowed now to enable sorting the full set of versions of a package
 - DependencyGraph and RequestedDependency have been removed

Integrate the "dub select" functionality in "dub upgrade".

Make some cosmetic changes to dub version selections. ...

- Adjust code style
 - Let "dub select" output a simple package->version map instead of package->{version, dependencies}
 - Rename dub.select.json to dub.selections.json.

Merge branch 'dustmite'

Preparing dub select command. dub select will select the currently used versions and write them to a file, so that dub can later use this information to rebuild this exact state. This will also be used to override dependencies with either branch versions or not matching versions (to resolve conflicts). (All of this if to be implemented). ...

Other changes:
- Added Version.UNKNOWN, which could be later used for undetermined package versions instead of ~master.
- Added Dependency to/fromJson.
- Added Dependency alias "*" for ">=0.0.0".