improve "make clean" and change some identifier names

  make "make clean" remove all *.vo and *.glob files, even the unknown ones

  change some identifier names to obey the convention that types are capitalized
  and objects are not.  Also change HProp, HSet, Trunc to IsHProp, IsHSet, IsTrunc.
Merge branch 'pull-request-2' of https://github.com/DanGrayson/HoTT into upstream

Conflicts:
	theories/Equivalences.v