Moved "Favorite tables" from session to browser-based localStorage.

After this commit:
- "Favorite tables" are no longer stored in session but in browser-based localStorage.
- If "pmadb" is available, then browser's localStorage will be updated with "Favorite tables" from pmadb.
- If "pmadb" is not available, then "Favorite tables" will be loaded from localStorage and new tables will be added to localStorage only.
 
Signed-off-by: Ashutosh Dhundhara <ashutoshdhundhara@yahoo.com>