make the "Save Problem" button a bit wider
added Module model class
more work on modules class/table - not quite working yet

Added a delta type for persisting a model object, so that
a migration will create the default "uncategorized" module.

What is still needed is a way to specify a default value for
an added column.  The default module id in problems will need
to be 1, because mysql treats "0" in an insert into an
auto increment column as a request to auto-generate an id, not
insert a literal 0. Fucking mysql.  So, we'll need the id
of the default module to be 1, not 0.
use 1 as module id for default "Uncategorized" module

More generally, allow default values on database columns.
added CourseSelection client model object, for selected Course/Module

Eliminated all places where a Course is directly added to the
Session (or expected to be in the Session).
TermAndCourseTreeView: change course nodes to contain list of Modules

ATM, module list is hard-coded to be just the default module,
and clicking on a module node doesn't do anything.  Next step is
to allow modules to be loaded dynamically when a course is selected.
add child modules of course nodes when they are selected

Right now, module list is still hard-coded to just be the
default "Uncategorized" module.  Next step is to load the
module list by RPC.
load modules when a course is selected
TermAndCourseTreeView: return CourseSelection, not just Course

This handles the possibility that a module of a course is selected,
rather than the entire course.
when a module is selected, only show problems in that module
force CourseAdminProblemListView to always load all problems in course
show assigned modules for problems in CourseAdminView
CourseAdminPage: allow inline editing of module name
Merge pull request #31 from daveho/module

support tagging exercises in course with module names