cylc poll-all: no options given then poll all

Closes #1177

Tests added.

Polls all tasks when no options are given at the command line.

Note that in my environment including on master tests/cylc-show/03-clock-triggered-non-utc-mode.t fails.
I have tested it and it does not appear to break when: polling all, i.e. no options, polling a family, i.e. family, cycle and -m and then polling a task i.e. task and cycle.

I have removed the 'retrying' and 'waiting' tasks from the polling.