search: quick fix for queries with leading space
search: quick fix for queries with leading space

* Strips leading/trailing white space from `p` argument to `/search`.
  This quick-fixes queries like `/search?p=+ellis` that were otherwise
  leading to "Showing records 1 to 0 out of 0 results" situations.

Signed-off-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

tiborsimko/invenio-search,tiborsimko/invenio-search,inveniosoftware/invenio-search,inveniosoftware/invenio-search