I have used Pylint tool to fix easily fixable issues. (Redmine issue: #3443)

It was impossible to store the 'state' attribute of user, group and filter objects into PostgreSQL database, because it was not correctly converted to boolean and SQLAlchemy failed to generate proper SQL command.

(Redmine issue: #3734)

The account registration process needed more work to get it into stable and usefull state:
* Changed validator for user login from email to string containing restricted set of characters.
* Renamed field 'Login (eppn)' to just 'Login'. It made no sense to be used that was for example with Basic or certificate based authentication service.
* Implemented sendind of confirmation emails after successfull registration to system admins and to the user that performed the registration. The emails are generated using Jinja2 templates.
* Implemented sending of confirmation emails after successfull account activation to the user and as BCC to system admins.
* Added missing rollback() calls to base View implementations to resolve SQLAlchemy errors after unsuccessfull database operation.

(Redmine issue: #3734)

Instead of deleting them entirelly, in many cases it might be better just to mark user accounts and groups as disabled. This commit contains following relevant changes:
* Updates in SQL data model for users and groups
* New base views, base form and form templates for generic changes of items
* Support for enable and disable actions in item forms and views (show,list)
* Support for enabled/disabled accounts in authentication controllers (disabled accounts will not permit login)

(Redmine issue: #3752)

(Redmine issue: #3734)

(Redmine issue: #3734)

After performing certain actions (item create/update/delete, login, locale change) an attempt will be made to SECURELY redirect user back to original page beforefalling back to default redirection target. (Redmine issue: #3734)

(Redmine issue: #3443)

User accounts can now be added into groups and can be designated as group managers. (Redmine issue: #3734)

(Redmine issue: #3734)

(Redmine issue: #3734)

Users may now choose prefered locale, which will be used for application language localization and datetime formating. (Redmine issue: #3734)

Users may now choose prefered timezone, which will be used when displaying time data. (Redmine issue: #3734)

PostgreSQL migration: Reimplemented DBAL, authentication layer and user management modules in Hawat.

Base on the previous work the DBAL in Hawat was reimplemented to use the new mentat.services.sqlstorage module and sqlalchemy backend. The authentication layer was rewritten to use the new dabase interface. The user management plugin was rewritten to use new database interface.

(Redmine issue: #3752,#3734)

(Redmine issue: #3734)