gstlal_feature_extractor + related files: added sine-gaussian waveform and made option available to use as basis function for feature extraction

datasource.py + pipeparts: added hacky fix to get around seeking issue for generating fake data at reasonable GPS times, done using the timestamp_offset feature of fakesrc

- because the parent class of the ratebin type is immutable, its out-of-place arithmetic operations don't necessarily return new objects since if the boundaries are identical the object can be re-rused.  but ratebin is not, really, immutable and its own out-of-place arithmetic operations assign values to the internal ._count attribute.  if the parent class' arithmetic methods return references to one or the other of the input arguments then ratebin's methods corrup the input object's count values.
- this patch fixes by ensuring a new object is created in the event the ._count atribute must be assigned a new value.

- fixes "... has no attribute .coincs_document" crashes
- addresses some lingering FIXMEs and removes some cruft

- new package cmath: elements that perform unary operations and handle complex and real floating point arithmetic. Elements included are cabs, cexp, cln, clog, clog10, and cpow.
- new element lal_trackfrequency: base transform element that attempts to measure the loudest frequency in a signal.

gstlal_feature_extractor_whitener_check: fixed issue with pipeline hanging after EOS, updated mkbasicmultisrc using new function args

- lal_smoothkappas: added filter latency option.
- lal_resample: simpler treatment of gaps. The complicated nonsense from before was unnecessary and messed things up.
- calibration_parts.py: function to remove lines and harmonics with a witness channel now works well.

- oops, copy-and-pasted, and forgot to splice the code in properly

- don't need to convert URLs to local filenames to use, that's what that function is for

- dump is a URL is set, not necessarily just because the data is there to dump

- reduce the number of distinct steps
- enable --density-estimate-zero-lag in marginalization step

- add --density-estimate-zero-lag

- fix a typo in a comment
- reduce the number of boolean operations in the extinction model fitting code

- .T050017_filename() moved homes and I forgot to update where the instruments come from

- fixes a bug in the filename construction code in the snapshot path
- uses CacheEntry to parse T050017 filenames instead of doing it by hand
- fixes a typo in a comment

- lal_complexfirbank:  Now handles latencies longer than filter length.
- lal_insertgap:  Compute offset when throwing away initial data as offset relative to the time when streaming started.
- calibration_parts.py:  remove_lines_with_witness should work now.