#297: move % delimiter for task ID to single place

Not safe for merging yet.

@hjoliver - have taken a go at moving the "%" signs out to a "." defined in one place (under the TaskID class). I believe I've caught 99.9% of the cases of hard-coded "%" signs for this.

The one thing I can't track down is where the names for tasks are set in the circles (tree?) plot view in the cylc gui. They are still coming out as TASK.CYCLE rather than TASK\nCYCLE. Any suggestions for what I've missed?

This passes the test battery, though I had to modify the reference logs to line up with the new format of TASK.CYCLE rather than TASK%CYCLE.

Let me know what you think.