Mention all src/parse files

src/parse/ is the first folder students will see, and it contains really a lot of files. We should help them understand how everything works out to avoid them just filling the blanks blindly.

Many of the files present in this folder will be present in all others, we should only need to mention them once here for good.

• Make a separation for TC-1 and TC-2
• Mention local.am and fwd.hh
• Mention and explain all "task-related" files (tasks.cc,hh, libparse.cc,hh)
• Mention tiger-parser.cc,hh
• Mention prelude.cc
• Mention tweast.hh,hxx and metavarmap.hh,hxx
• Mention test-*.cc
• Explain what files are / can be generated (parsetiger.cc,hh,output,xml,html, location.hh, position.hh, scantiger.cc,hh)

Maybe we could also mention *.lo and *.o ?