gstlal_inspiral_summary_page: add horizon distance plots back to summary page but plot them on a image pagination component so that they will not be fetched all at once and slows down the page.

Note: this depends on gstlal-visualisation/ligo-scald!36.

gstlal_inspiral_pipe and inspiral_pipe.py: replace gstlal_insprial_plot_psd_horizon with gstlal_inspiral_plot_rankingstats_horizon, and temporarily remove horizon distance from summary page since there will be too many horizon distance plots.

minor bug.

horizon history from multiple ranking statistic files.

renamed gstlal_inspiral_plot_psd_horizon --> gstlal_inspiral_plot_rankingstats_horizon and use plots.horizon for plotting.

* fix itacac, lloid element name from rebase
* skip test_element_registry tests due to function aliases in pipeparts

stream.py: replace GObject.MainLoop() -> GLib.MainLoop(), remove GObject.threads_init() to address deprecation warnings

Stream: add functionality to get elem by name, post bus messages. update lloidhandler.py to leverage this

* merge StreamMap/Stream into a single class
* store caps within Buffers returned from bufsink()
* reflect changes in gstlal_inspiral, lloidparts.py

* fold in state/DQ vector support in Stream.from_datasource
* expose setting pipeline state via stream.set_state(state)
* support operations on groups of keyed streamed via StreamMap
* allow callbacks via EOS messages where message types are not relevant
* support x-lal caps when pulling buffers from appsink
* support AppSync functionality for synchronization via StreamMap.bufsink