Prepare bisection search for runtest integration

Prepares bisection_search.py for run-test integration.
Introduces a --raw-cmd switch which accepts a full dalvikvm
command.

Fixes few bugs.

Test: ./art/tools/bisection-search/bisection_test.py
manual testing

Change-Id: I0272d21fe1e73278837bce76ad3eef632993fbe2