Added quoting of import paths

If --main-file was given for "dub test", prefer a normal library configuration over a "unittest" one.

Use an existing "unittest" configuration for "dub test" by default.

Add back version output for --help and improve SemVer conversion of the GIT describe output.

Rename badly named PackageManager.get to storeFetchedPackage.

Fix "mainSourceFile" to be emitted for Project.addBuildSettings with the "shallow" parameter set. ...

Fixes "dub test" for library targets.

Change order of command class declarations to match their order in the help screen.

Also fall back to "dub -b unittest" if there are no source files in the selected library configuration.

Fall back to "dub -b unittest" when "dub test" finds no library configuration.

Let --nodeps work for any command of the build/generate category.

Remove log message previously used for debugging.

Merge branch '0.9.20'

Work around DMD associative array bug. Fixes #179.

Fix running "dub test" on an explicitly named package.

Implement the "test" command.

Fix appending absolute paths for the working directory.

Tweak help screen formatting and add a few short options.

Group commands by category in the help screen + add a skeleton for the "test" command.

Fix parameter handling of the "init" command.

Fix missing log argument.

Add --force switch for "dub run" and "dub build" and fix --rdmd.

Make sure the target binary gets deleted when the linker has failed.

Merge branch '0.9.20'

Update change log and bump version number.

Output a warning if no main source file is defined.

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

Let --annotate work for all commands.

Defer initialization code so that displaying help works immediately and without the danger to fail.

Revamp the command line interface with cleanly separated command implementations.

Fix Path.toNativeString() for empty paths (was missing the ending slash).