KT-1545, KT-3161 KDoc basic lexer, parser and formatter

Basic implementation of KDoc lexer, parser and formatter (now only striping leading asterisks).

I Have some questions about JetFormattingModelBuilder.createModel (see http://devnet.jetbrains.com/thread/444830?tstart=0 )

Another question about KDoc asterisks stripper: what do you prefer: copy crazy implementation of DocCommentLexer.AsteriskStripperLexer or use my "JFlex longest match hack" (see KDoc.felx)?

Building & all tests passed.