HUE-1798 [impala] Improve database dropdown

Added chosen to Impala and Beeswax
Restyled a bit the side bar on Beeswax and Impala
Reintroduced last database saving
HUE-1831 [beeswax] Switch view sample and open table in navigator

Icons are switched now
[beeswax] Fix explain query test API and test_explain_query_i18n test
HUE-1823 [beeswax] Re-integrate resource lists in the editor

Bug in multiform handling on front end.
HUE-1825 [beeswax] Re-add filebrowser to file resources
Merge remote-tracking branch 'upstream/master' into testing-abe