Huge amount of work towards making Mentat executable from within the cloned Git repository.

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)