Add a new RepositoryGridFilterManager to the Tool Shed framework to support filtering the repositories displayed in the many Tool Shed grids.  The current filters are CERTIFIED_LEVEL_ONE, CERTIFIED_LEVEL_ONE_SUITE and CERTIFIED_LEVEL_TWO, CERTIFIED_LEVEL_TWO_SUITE.  The "level one" filters display repositories or suites that have been certified by the Tool Shed's install and test framework.  The "level two" filters are not yet supported (the query enhancements are trivial, but not yet done) since no repositories in the test or main Tool Shed have been certified at this level (this level requires reviews and approvals by IUC members).  When set, filters are stored in session cookies.  Filters are easy to set.  The Javascript event handler (e.g. checking a filter checkbox) would make a call something like: trans.app.repository_grid_filter_manager.set_filter( trans.app.repository_grid_filter_manager.filters.CERTIFIED_LEVEL_ONE ).