Removed deprecated gwpy.table modules

This PR introduces a backwards-incompatible removal of multiple modules/functions related to augmenting the glue.ligolw table objects with useful functionality. The removed modules are

• gwpy.table.lsctables
• gwpy.table.utils
• gwpy.table.rec
• gwpy.table.rate
• gwpy.table.io.ascii

Basically this removes all functionality associated with importing ligolw lsctables objects from gwpy, and the unified I/O that used to be attached to them, e.g. you can no longer do anything like

>>> from gwpy.table.lsctables import SnglBurstTable
>>> t = SnglBurstTable.read(f)

instead you should do something like

>>> from gwpy.table import EventTable
>>> t = EventTable.read(f, format='ligolw.sngl_burst')