Fixed the Taable and SplitTable classes

* Changed the XPATH expression and made the search for elements start from a
root element instead of from DOM root
* Renamed occurances of browser to sel in the tasks.py page
* Removed the is_displayed() method and replace occurances with
sel.is_displayed()
Fix accordion locator to avoid name collisions
* example, "Catalog" was matching "Catalog Items"
Catalog tests and supporting code
* Catalog model
* multiselect and dispatching
Fix navigation to new Catalog to select "All Catalogs"
Start adding forms and class for Catalog Items
Merge branch 'master' of github.com:RedHatQE/cfme_tests