Series import: move configuration of the site parsers to database

[php-coder]

At this moment, site parsers configuration is staticly defined in the application.properties file(s). It means that when we add one more parser or changes the property of one of the existing, we have to restart the application.

The first issue, that once broke the site already, is that ansible role doesn't support app.site-parsers* properties yet (see #929). If we move these properties to database, we won't need such a support at all.

The second issue is that restarting of the application slow us down when we working on the adding a new site parser. If we would have such configuration in database, we won't have this difficulty and adding a new site parser (or fixing the existing one) will be much faster. In this case, we should read the configuration from database not just once, during application startup, but for every import request.

[0pdd]

@php-coder the puzzle #982 is still not solved.

[0pdd]

@php-coder 2 puzzles #982, #983 are still not solved.