Added rudimentary support for the --arch= option and moved build type flag generation to a common place.

Avoid use of deprecated functions + fixed package installation.

"dub build" and "dub run" are now also executed using the generator system (RdmdGenerator).

Implemented basic multi-compiler support (with only a dmd implementation right now).

Added @property to several getter functions with field names.

Handling missing package.json more gracefully (without a crash) + some trace log messages.

Fixed up to date check when checking for validity of an installed package.

Renamed Application to Project and put it into its own module + added a stub MonoD generator.