lal: add time series conversion funcs

- add XLALConvertREAL8TimeSeriesToREAL4()
- add XLALConvertREAL4TimeSeriesToREAL8()
glue.ligolw.dbtables: add _CONDOR_SCRATCH_DIR Easter egg.
lalsimulation: edit some comments.
ProgressBar: add .increment() method
PEP8