tstart tend refers to signal properties, so is only used when relevant.
Otherwise use the LAL parameter min/maxStartTime

It seems the tests have been failing, but only falling out of range by
~0.11 rather than 0.1. This increases the allowed range to 0.2

This makes the MCMCGlitchSearch a subclass of the more general
MCMCSearch

Create a separate class for pure ComputeFstat wrapper, then gives this
as a parent to the other searches. Ultimately, this will allow the use
of the ComputeFstat class without needing the glitch part, for example
for a transient search.

Removes the fully-coherent search which was just a wrapper to CFS_v2 and
all of the `slow' methods which used command line arguments rather than
the python interface.