Temporarily re-allow '-' in arcyd configs

Test Plan: visual inspection, testbed doesn't seem to work for me

Reviewers: mseplowi, jevripio

Reviewed By: mseplowi

CC: arcyd

Differential Revision: https://all.phab.dev.bloomberg.com/D108570
Fix Arcyd to allow dashes in config names

Summary:
It's common for repositories to have dashes in their names, it seems
useful to preserve these in the config name without mapping them to
underscores.

Fixup the doctest to allow dashes, add some justification for the
CONFIG_NAME_REGEX.

Test Plan: $ ./precommit.sh

Reviewers: cbailey, mseplowi

Reviewed By: cbailey

CC: arcyd

Differential Revision: https://all.phab.dev.bloomberg.com/D110494
'arcyd fsck' checks repo config names are valid

Summary:
Make sure that invalid repo config names don't slip into the config
repository and also validate repositories that were created before the
validation code landed.

This may point to other changes that need to be made to the
CONFIG_NAME_REGEX.

Test Plan:
$ ./precommit.sh

check that invaild names are reported
$ ./testbed/arcyd/test_shell.sh
  $ cd ../arcyd2/config/repository
  $ cp localhost_fs1_origin localhost_fs1_origin.1
  $ cd ../..
  $ arcyd fsck
  .. errors as expected ..

Reviewers: cbailey, mseplowi

Reviewed By: cbailey

CC: arcyd

Differential Revision: https://all.phab.dev.bloomberg.com/D110528