gentmaint-log: print last 3 logs by default

* gentmaint-log: print last 3 logs by default:
  * was 10
Call gentmaint-version with option header if called to print a header

* Call gentmaint-version with option header if called to print a header:
  * gentmaint-version may be called by other scripts to print a header
  * if so, also print the start date/time of the code
  * if called by hand, just print version info
gentmaint-version: print code start date/time only when called by another script
Updated copyright
Added Initial/Final size labels to gentmaint-clean

* Added Initial/Final size labels to gentmaint-clean:
  * disc size of /var/log/portage/ before/after compressing log files