Added encode_pg_and_html subroutine that encodes all html, ev3 and pgml special characters.  I also made a bunch of changes to different files to use the new subroutine.
Merge branch 'master' of https://github.com/openwebwork/pg into encodebug2

Conflicts:
	macros/PG.pl
Fixing somethings and reverting some unintended changes.
Fixing my fixes.
More polish on encoding pg and html.
Reverting unneccessary changes.
Reverting additional changes.
Merge pull request #168 from goehle/encodebug2

Encode PG Special Characters