Simplified reading timeseries from cache
This PR (again) simplifies reading a TimeSeries
from a Cache
of files, by removing the overloaded gwpy.timeseries.io.cache.read_cache
method in favour of a simpler call to gwpy.io.mp
(see #590, #602).
This also deprecates the resample
and dtype
keywords, bringing TimeSeries.read
in line with TimeSeries.fetch
in that it just loads the data, and doesn't do much else.