Add ability to specify AS-annotation combine operations

[ldgauthier]

This should be possible in the FeatureDataSource using code similar to https://github.com/Intel-HLS/GenomicsDB/blob/master/src/main/java/com/intel/genomicsdb/importer/extensions/VidMapExtensions.java#L69

We don't have a use case for this right now, so I'm calling it low priority. I started a draft at ldg_addAScombineOp but it needs tests.

[droazen]

@ldgauthier Is this one done?

[ldgauthier]

No, but it's not something I need.

…

On Mon, Feb 4, 2019, 4:01 PM droazen ***@***.*** wrote: @ldgauthier <https://github.com/ldgauthier> Is this one done? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#5250 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AGRhdDLmv_QSgKJ3twW3WiJb4Kf2XEGCks5vKJ-LgaJpZM4XEjqF> .

[ldgauthier]

Closed via #4947