(Redmine issue: #7632)

(Redmine issue: #7632)

Original idea wa to use Docker for this purpose, but it turned out full
featured virtual server will be much better suited for this task due to
the comlexity of the whole environment.

(Redmine issue: #7041)

(Redmine issue: #3387)

(Redmine issue: #3443)

(Redmine issue: #3387)

(Redmine issue: #3387)

* 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)