Arcyd: add reset and pause buttons to dashboard

Make it possible to pause and reset Arcyd via the main dashboard,
requires some implementation on the part of the embedder.

Will aim to reduce this burden in future commits, when Arcyd gets a
standardized file layout and commands for managing data.

Test Plan:
visually inspect $ ./testbed/arcyd/status_html_testbed.sh
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh