API documentation for Project getters
Additional convenience methods on Project for configuring the .sbt files processed.

The Project.setSbtFiles and addSbtFiles methods combined with the current sbt version
available from ComponentMangaer.version (suggestions for a better location are welcome),
should make it straightforward to load different .sbt files based on the sbt version.

Fixes #467.
Don't try to automatically detect a main artifact when packaging=pom.  Fixes #636.

For the rare case where a main artifact is expected, add an explicit jar()
to the dependency declaration.
Docs: cleanup a few backticks for inline code
Configurable conflict manager and corresponding documentation on conflictManager, dependencyOverrides, and force().  Fixes #603.