support FlyCircuit 1.2

[jefferis]

Essental:

• support for FlyCircuit 1.2 ids (probably keeping track of which release contained which ids)
• remove all use of gene_name or idid as an id (these both seem to have been retired)
• update flycircuit-ids documentation accordingly to better explain the mess

Desirable:

• map to canonical side
• process for NBLAST

Hopefully:

• package SWC data in FCWB space
• figure out annotations for new neurons (at least those that match existing annotations)
• complete annotation in conjunction with EM data?