refactor batch processing infrastructure

[Robert Jäschke]

Currently, there are several Perl scrips that are started by Cronjobs in the background to compute several things, e.g., tag counters, similarity measures, etc.

These scripts are cumbersome to install, configure, and maintain, e.g., changing the database connection or turning off a script is difficult. In addition, the only output they deliver are emails upon errors. It would be better, if there would be a daily mail that provides some status from the scripts (e.g., how often they were run, how much data they computed, etc.). There should also be some logging, etc.