lalinference_pipe_utils.py: Change of names of modules and a ContentHandler. Minor changes in readLValert.

 - Change names for modules as follows, utils->ligolw_utils and series->lalseries.
 - Change the name of the ContentHandler for coinc.xml into LIGOLWContentHandler.
 - Stop importing modules which are not used in readLValert and unify the indentation rule in readLValert.