fix(livesearch): removed custom queries with ege* functions

There was a long standing todo to remove the custom queries in the
livesearch page_handler with elgg_get_entities* functions.

as requested in #6792
- [x] change commit type to "fix"
- [ ] add group picker to theme_sandbox > forms
- [x] test changes manually from theme sandbox
- [x] resubmit against 1.9 branch

I changed the default autocomplete in the theming sandbox to support groups and friends. Users can be tested with the user-picker.