installation: jinja2utils and requirements upgrade

• Upgrades python dependencies to latest versions and fixes compatibility issues with Jinja2/MarkupSafe packages. (addresses #1476)

• NOTE run pip install -r requirements-flask.txt --upgrade and pip install -r requirements-flask-ext.txt --upgrade. You might need to clean pip cache and build directories (rm -rf ~/.pip/cache/* ~/.pip/build/*).

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>