Improve query filtering for Search

- there was a crash when inputing "w" then "-" then "-". This
crash was due to the InputFilter which got some strange indices
from the BaseInputConnection.
- so now we are doing our own filtering before sending the query
to Sqlite. We only keep Letters / Digits / Spaces.

Change-Id: I66dcbebeec9217cf8fd65a16b10fe2304d98cf58