This commit brings in considerable amount of work. When working on this issue everything was so tied together, that I have abandoned all attempts to split it into multiple commits. There are following changes and more:

* Implementation of lightweight chroot for containing the application in single directory tree.
* Design changes in scripts and daemons to implement the lightweight chroot.
* Many configuration file changes to make everything work properly.
* Makefile additions, new targets related to running
* Updated development documentation page.

(Redmine issue: #4216)

Currently only built-in Flask commands run, shell, etc. are available. It can be used to launch development web server, which is now documented in development documentation page. (Redmine issue: #4216)

Documentation, build procedures...almost everything was revised and rethought.  (Redmine issue: #4216,#3387,#3361)

* Merged pylint and pyflakes tasks for simplicity,
* Fixed broken clean task.
* Updated development documentation to include Grunt as prerequisite.
* Few additional minor tweaks.

(Redmine issue: #4216,#3387,#3361)

Following big improvements were made to make the development more easier:

* Created the 'setup.py' script to support native Python packaging with setuptools and pip.
* There is a new target 'make develop', that will bootstrap the Python virtual environment, install all production and development requirements and install the whole project in editable mode.
* Revised the dependency installation targets.
* Big facelift of makefile help target.
* Added target for build environment cleanup.
* Added target for initialization of new translations of Mentat and Hawat.
* Added target for building locally Python packages.
* Added target for building locally Debian packages.
* Updated documentation page for developers.

(Redmine issue: #4216,#3387,#3361)

The database migrations for IDEA event database *mentat_events* are now implemented. I have moved this issue to the next release, because there is code already merged in the current development branch that depended performing the migrations on target system. It was a choice of either removing that commit, or going forward with implementation. I have decided to implement it immediately, because this issue is blocking many more features.

The implementation is again based on Alembic tool, which is already being used for migrations on mentat_main metadata database. It is however separatelly configured instance, merging both instances into single one would require considerably more amount of research and work.

I have also updated accordingly manual pages regarding installation and upgrading. Very important bit of information was stamping the database with latest migration revision after clean installation.

(Redmine issue: #4230)

Moved some content from website to autogenerated documentation to prevent from repeating the same content on multiple places. Added information about versioning and tagging. (Redmine issue: #3361)

Improved documentation with focus on possible developers, so the Overview and Development section were greatly improved. (Redmine issue: #3361)