Arcyd: better checking with global constants

Change abdt_reporeporter to use module constants instead of class
constants when constructing it's dict - they are more amenable to
static checking.

Test Plan: $ ./precommit.sh

Introduce references to non-existant class constants, observe no
errors during static checks.

Introduce references to non-existant MODULE constants, observe errors
during static checks.
Arcyd: HtmlFormatter uses <pre> for text

Use <pre> to preserve formatting when outputting text.

Test Plan: $ ./testbed/arcyd/status_html_testbed.sh
phlgit_merge: add TODO - test squash no changes
Arcyd: note current branch and more on fail

Add the facility to note the current branch and additional context for
all statuses.

Add tests to ensure that the branch context is handled correctly.

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/status_html_testbed.sh