add support for Owner Name in case list

no UI yet, currently done by typing in #owner_name
parent/#owner_name, etc. also supported
fix xpath for group_name

- use @owner_id instead of owner_id (in casedb)
- use current()/@owner_id when embedded in another context
- use explicit comparison count(...) != 0, since xpath doesn't do
  falsiness
add candy coating to UI for Owner Name in case list
Merge branch 'master' into owner_name
Merge pull request #3662 from dimagi/owner_name

Owner name in the case list