Revision 872

Added comments.  There is still an annoying problem
that it is possible for the user to insert a problem
that has an empty directory address (e.g /prob3.pg, 1)
if they use "Choose problem" before ever using "Select set"

Viewing the entire set, saving the set and viewing individual problems from the local library (as opposed to the problem library on webhost) remain to be implemented.

-- Mike