#94 - cylc gui suite error log integration

This improves the integration of the suite log 'error' type messages within gcylc and closes #94.

What it does:
  * cuts down error notification within cylc to a minimum to avoid swamping the user (now only for genuine errors/problems) - this is a compromise, as the Python logging module does not do what we want
  * incrementally communicates error text to gcylc (avoiding large communication overhead)
  * adds an error image to the bottom right of the gcylc info bar if there is any error content
  * hovering over the error image brings up some error text lines
  * clicking on the error image brings up the Suite Error subprocess output as in the menu
  * clicking on the error image sets it to insensitive, until more errors arrive (acts as notification)
  * gcapture/subprocess output capture has been tweaked to include a progress bar in lieu of "Remote invocation...." type messages
  * alters test-battery reference logs given the change in error notification, because I thought it was necessary (I think it isn't).

It isn't a console, but I think in some ways this is better.

@hjoliver, please review.