Implemented prototype built-in help pages for events/sear4ch and events/show endpoints. Improved the help pluggable module to autodiscover help pages. Improved autogenerated Sphinx documentation for events pluggable module. (Redmine issue: #3361)

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)