GG B.1. - Improving OGP to allow setting custom log file about open-geo-prover HOT 2 OPEN

Made first set of revisions for this task: r253 (main trunk), r254 (GeoGebra 
branch) and r255 (Area method branch). They contain necessary code changes that 
are preparations for main work on this task and they are related to 
improvements of custom files so they could use any directory for source or 
destination of files.

While main task is not fully completed, in order to be able to correctly create 
log files, read input files and create output reports, in Eclipse environment 
it is necessary to set-up working directory in each single run configuration. 
This is necessary because these files are still created relatively to current 
working directory. For working directory proper workspace location has to be 
selected (where 'input', 'output' and 'log' directories reside).

Previous title: GG A.2. - Improving OGP to allow setting custom log file
Remaining work is for stage B.1.