hgview #8729 be more robust in gview sources with "__pkginfo__" module [validation pending]

Make any "import __pkginfo__" found in hgview sources be surrounded by "try/except" do it does not prevent hgview from running if it does not exists.

Make setup.py do the copy of the __pkgfile__.py file into the hgview package directory (do not forget to remove it at the end of the setup.py file)