move PageStack to client.model package (where it was supposed to be)
get rid of comment template for overriding methods
added ProblemSubmissionHistory model object

This will be the basis for refactoring UserProblemSubmissionsPage
into separate views (all of which visualize the
ProblemSubmissionHistory object.)
factored submission history slider view out of user prob submission page
factored problem text view out of UserProblemSubmissionsPage
support parallel execution in BatchMain (multicore FTW!)
hmm...multiple threads seem to produce unpredictable results

Need to investigate further.  For now, just use a single
worker thread.
added RepoProblemRating model class

This will allow repository users to rate repository exercises.
fix name of db table for RepoProblemRating class
add RepoProblemRating table to list of tables for repo db
fix classpath
Merge branch 'master' of git://github.com/daveho/CloudCoder