Add sbt command to clean all class files

[farquet]

I noticed that running clean in sbt, even followed by cleanFiles keeps a lot of class files around. If you are switching between JDKs, you will hit bad class file versions and you will have to remove them manually somehow. Currently, I simply do

find . -type d -name 'target' -prune -print -exec rm -rf {} ';'

but that's dangerous and removes more than necessary. We should introduce an sbt command renaissanceClean that properly removes those class files.

Reference : https://stackoverflow.com/questions/4483230/an-easy-way-to-get-rid-of-everything-generated-by-sbt

[vhotspur]

I found this old issue in SBT tracker where it seems that it is actually not an issue at all ;-)

[...] been discussed on the mailing list before with the same conclusion as the linked StackOverflow question. If you really want a clean cache, [...] you don't need to rely on the build tool's clean. [...]