Cleans bunch monitor. Tested recently added buffer.

 - flush again replaced by open-close.
 - open-close enables to write back from lsf node to afs and
   allows to look at the data while simulation is ongoing.
 - trouble with huge filesize due to open-close statement after
   every turn is now under control with the buffer -> less file
   accesses and open-close statements.
Slims down slice monitor. Adds buffer to it.

 - Particle monitor yet to be cleaned.