base: move here the script for autocomplete

* Moves the script for autocompletion from groups module to
  base module.

* Modifies the autocompletion script to automatically enable
  the functionality after the page loading.

Signed-off-by: Leonardo Rossi <leonardo.r@cern.ch>
We can add the value to the original field, for example something like: `$('[name='+field_id+']').val(data[data_key])`