Table insertion and manipulation now works in lists

This pull request addresses issue #403 and partially addresses issue #139 by allowing tables to be inserted and manipulated within lists.

Previously, table insertion did not work at all for lists, and if you tried to insert a table with a selection in a list, the table would be inserted at the end of the document instead. This pull request fixes this issue by now allowing tables to be inserted at any point within a list or sublist. In addition, once a table is inserted into a list, it will properly indent and outdent with the list when the indent and outdent tools are used. This will work even if multiple tables are inserted at the same or at different points in one list.

A reoccurring issue I found with tables in a list was that when a table was inserted at the end of a list or sublist, the user could not click under the table to continue to add points to the list after the list item containing the table. To fix this, I put in checks when a table is inserted, indented, or outdented in a list to ensure that space exists under the table so that the list can always be continued.

I also added ten tests to the unit tests for table insertion, indention, and outdention in a list, including tests for the issue of continuing a list after a table that I mentioned in the paragraph above. I have confirmed that these tests all pass in FF 21, Chrome 27, and IE 6-10.