Flask: integration of legacy unit tests
- Adds new @with_app_context(...) decorator for ensuring application context in functions called from command line before they will be ported to inveniomanage script.
- DEPRECATED flaskshell will be removed and replaced with with_app_context decorator or application factory usage.
- Fixes UserInfo object that was returning uid == 0 instead of -1 for guest users (webuser_unit_tests.py).
- TODO check inveniocfg_upgrader for upgrades from non-Flask based installations.
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>