Change default file extension for omicron trigger files to HDF5 files

Created by: eagoetz

Omicron will soon only output ROOT and HDF5 files (with extension h5). Current versions output these and xml.gz files, but moving forward we should default to the HDF5 file format.

Note that internally, the Omicron HDF5 file does not have bandwidth or duration, for example. These can be derived from the fstart and fend or tstart and tend parameters respectively.