Bug 31399: Set focus on first input when adding a new classification source, filing...

Bug 31399: Set focus on first input when adding a new classification source, filing rule, or splitting rule

This makes sure the cursor/focus is always in the first form
field when adding an entry on the classification configuration page.

* Got to administration > classification sources
* Verify for each of the three "New ..." buttons on top that
  the entry form has no focus on any field
* Apply patch
* Repeat testing the new forms and the focus now should always
  be in the first input field of the entry form

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>