Cleaned up Series ASCII I/O methods
This PR cleans up the ASCII I/O methods for Series
subclasses (TimeSeries
and FrequencySeries
mainly), highlights include
-
gwpy.io.ascii
moved togwpy.types.io.ascii
- ASCII registrations for sub-classes moved to
gwpy.<subclass>.io.ascii
The new structure mirrors much of what was written for HDF5.