search.py: add Finder class, regexp find and use only placeholders

* Finder class should make it easy to search through the sqlite3
  from pyhon, not only CLI.
* regexp find treats the parameter arguments as python regexp
* using placeholders in the queries to avoid breakage with
  (double)quoted CLI arguments

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>