[impala] Impersonation support

Refactor use_sasl and use_impersonation in OpenSession.
HUE-1566 [impala] Auto complete not wide enough

The autocomplete window will be now limited by its content
Items are selectable on click
Improved autocomplete usability (spinner) and backend calls (10 minutes of metastore data validity)
[metastore] Adding icons
[beeswax] Fix permissions of auto queries not linked to a design
HUE-1616 [core] Diversify Oozie icons for dashboard and editor

Added new icons
Renamed other oozie icons
[core] Fix LDAP config