flag/capability for BuildConsensus to keep certain fields

[Former user]

I frequently find that I have fields at the BuildConsensus step that I don't want to lose.

Right now I can hack this a little with "--pf FIELD --prfreq None " but i can only keep one field that way, and it gets renamed to primer, and I simultaneously lose the functionality of what that flag is meant to do.

I can see how there must be limits on this, specially when CONSCOUNT is high, but maybe there's room for limited support of this feature. For the emulsion analysis we often are doing two passes for BuildConsensus: one with PCR dups, and another for mRNAS within the same droplet.

[Jason Vander Heiden]

I'll add the copy fields (--cf) and copy actions (--act) flags to BuildConsensus, as per the functionality in CollapseSeq. This was already on my todo list as well.

[Jason Vander Heiden]

Added --cf <fields> and --act <actions> arguments, with action choices of 'min', 'max', 'sum', 'set', and 'majority'. 'set' and 'majority' also add a <field>_COUNT and <field>_FREQ annotation, respectively.