* policies/expression: migrate to raw python instead of jinja2
* lib/expression: create base evaluator, custom subclass for policies
* core: rewrite propertymappings to use python
* providers/saml: update to new PropertyMappings
* sources/ldap: update to new PropertyMappings
* docs: update docs for new propertymappings
* root: remove jinja2
* root: re-add jinja to lock file as its implicitly required
