(Redmine issue: #7041)

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)

* The maintenance apache site used bootstrap.min.css downloaded
  from the CDN. This is discouraged according to lintian:
  $ lintian-info -t privacy-breach-uses-embedded-file
* The canonical way to solve this issue is to use the corresponding
  debian package providing the referenced file, which does indeed
  exist: 'libjs-bootstrap'. In hawat, which this maintenance site
  replaces during downtime, corresponding css file is included
  statically, so adding another dependency just for maintenance
  site is an overkill. Both the static hawat version and the version
  in current debian's libjs-bootstrap are from Bootstrap v3.4.1,
  but the maintenance site is based on v4.3.1, so just download
  that and include it statically. The misversioning might be a typo
  and then either reusing the hawat's version or changing both
  to use the debian's packaged one might be a better way.

* The maintenance apache site used bootstrap.min.css downloaded
  from the CDN. This is discouraged according to lintian:
  $ lintian-info -t privacy-breach-uses-embedded-file
* The canonical way to solve this issue is to use the corresponding
  debian package providing the referenced file, which does indeed
  exist: 'libjs-bootstrap'. In hawat, which this maintenance site
  replaces during downtime, corresponding css file is included
  statically, so adding another dependency just for maintenance
  site is an overkill. Both the static hawat version and the version
  in current debian's libjs-bootstrap are from Bootstrap v3.4.1,
  but the maintenance site is based on v4.3.1, so just download
  that and include it statically. The misversioning might be a typo
  and then either reusing the hawat's version or changing both
  to use the debian's packaged one might be a better way.

Sometimes the downtime due to the upgrade or error can be noticable to the users, so the well behaving application should have some kind of maintenance mode to inform the users. This commit contains simple web page with capabilites of variable substitutions (to insert separately generated timestamps about the duration of the downtime), an example site configuration for Apache web server and updated documentation page about sustem upgrade. (Redmine issue: #4277)

The makefile target 'develop' now pre-builds web interface artifacts. There is a new example configuration file for Apache2 that demonstrates the necessary configuration for Git installations. There is a custom WSGI script file for easier web interface installation from Git. (Redmine issue: #4216)

(Redmine issue: #3387)

(Redmine issue: #3387)

(Redmine issue: #3387)

(Redmine issue: #3387)

There are two Apache example configurations now, first is an example for Shibboleth SSO authentication, second is an example for Basic authentication. Using these two examples (especially the latter) it is possible to very quickly set up demonstration installation. The installation page was updated accordingly to reflect new installation options. (Redmine issue: #3387,#3361)

(Redmine issue: #3387)

This commit represents huge amount of work and introduces new Python-based version of Hawat web user interface for Mentat system. It is built on top of the great Flask framework. Currently it is still work in progress and many features are implemented only as dummy stubs, however the core functionality is almost finished. Following is a list of current key features:

  * Focus on modular architecture using Flask`s blueprint feature.
  * Multi-layered configurability (defaults, multiple file overrides).
  * Plugin system.
  * Internationalization support.
  * Support for multiple authentication systems.

This commit provides working albeit hollow starting point for future web interface development. IT IS NOT READY FOR PRODUCTION USAGE!!!

(Redmine issue: #3734,#3361)