Implemented 'compound rule' logic in the FilterTool's script support.

Implemented 'compound rule' logic in the FilterTool's script support.

 * Previously the script was limited to doing 'OR' comparisons on various
property sets (what I call here filters). Now, by providing each filter
with an id, you can use these id's to define a compound rule.

 * Documentation is severely lacking on this end at the moment, but I hope
to have a good explanation up soon.  I think this interface could provide
a powerful flexibility in querying BAM files for very specific cases for
further analyses.