gw_summary: minor bug fixes
utils: added re_channels
triggers: use etg.lower()
DataSummaryPlot: replace '-' in plot params
plot.bultin,plot.registry:

    - added TriggerTimeSeriesSummaryPlot to generate time-series plots
      from trigger sets (discontiguity problems)
    - re-worked registry.register_plot to the same as for the tabs
plot.builtin: fixed xlim, made trigplot nicer
tabs: fixed two bugs
data: use cache=None as default

    - this allows tabs to cheat looking for data if they have already
      loaded it from other means
    - the only use of this so far is loading 'time-series' from ihope
      triggers and making sure the tab.process action doesn't go looking
      in the frames for custom channels
TriggerSummaryPlot: bug fix in add_loudest

    - only add_loudest for non-empty tables
    - fixed call for x-y plots (i.e. no colour)
SimpleStateTab: re-worked channel access

    - added get_* instance methods for channels, triggers, and flags
      instead of the arbitrary properties from before
    - also abstracted plot scaffolding out of the build_state_html
      method for sub-classes to use.
tabs.ihope: added widget for Daily Ihope
tabs: fixed ifo[0] bug lingering from older code