improved labeling

Change-Id: I76a28a5287c5d62d32b4153aa247dac075cad2be
bug fix - no longer clearing metadata in ProxyColumn.dataUnavailable()

Change-Id: Icdaefe3a8d159b336c08e7536f33173c6c5078d7
organize imports

Change-Id: Ia1c1cbeacad00f8cdbcb0bd9610711c2f806a008
Finished implementing aggregation code.
Added "common" aggregation method.

Change-Id: Ic9d741b7524d5de1d2cae9826b16bf37464f0a00