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 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)

With future improvements of database schema there must be a mechanism for performing database migrations. Problem is we have two databases, one accesed via SQLAlchemy and the second directly via Psycopg2. I have selected to use Flask-Migrate plugin built on top of Alembic to perform metadata database migrations. (Redmine issue: #4230)