gstlal_feature_extractor: changed method of local frame caching from copying over frames to generating new frames containing only channels needed for analysis, added auxcache.py to gstlal-ugly to facilitate this, and updated Makefile.am to reflect new file

- a variety of import related adjustments and fixes

- ensure pipeline is in READY state before calling this function

- using mmap()ing is the default

Replace datasource.mkbasicsrc with a stripped down version with elements only necessary for the hoftcache pipeline

- the muxer's sink pads are already thread boundaries, there's no need
  for a queue element between the resampler and the muxer

hoftcache.py: write separate channels out to separate files to prevent missing channels from being an issue