Enable submitting inline comments

Summary:
Added a --attach-inlines option to aoncmd_comment.py that, when provided, will
cause arcyon to also attach any inline comments to the submission.

Test Plan:
given a comment with any inline comments, run arcyon comment id
--attach-inlines --action comment, and the comment should be submitted along
with the inline comments.  Running without will not submit the inline comments.

Reviewers: jevripio, jfalgout

Reviewed By: jevripio

CC: arcyd

Differential Revision: https://all.phab.dev.bloomberg.com/D98836
abdi_repo: Reformat lines to look nicer
phlsys_fs: add read_text_file() for convenience

Make simple and safe reading of small text files easy to inline by
wrapping it up in a helper function.

Test Plan:
Exercised in later commits.
Add phlgitx_ignoreident for easily ignoring idents

For non-interactive uses of Git repositories, it can be undesirable to
allow the 'ident string' functionality as there are some edge-cases that
may require manual intervention.

Provide a tested utility for doing this easily.

Test Plan:
Add test driver and
$ ./precommit.sh
Arcyd: use phlgitx_ignoreident to ignore idents

In a few repositories, Arcyd has had problems where files with expanded
ident strings have been checked in.  This means that phantom local
changes will be reported and we're unable to move between branches.

Use the new phlgitx_ignoreident utility to ignore these idents.

Test Plan:
$ ./precommit.sh

Check that new repos are ignoring ident and that 'arcyd fsck' will
repair the attributes file.
$ ./testbed/arcyd/test_shell.sh
    $ cd ../arcyd2
    $ arcyd fsck
    $ rm var/repo/localhost_fs1_origin/.git/info/attributes
    $ arcyd fsck
    'var/repo/localhost_fs1_origin' is not ignoring ident attributes
    use '--fix' to attempt to fix the issues
    $ arcyd fsck --fix
    'var/repo/localhost_fs1_origin' is not ignoring ident attributes
    setting var/repo/localhost_fs1_origin to ignore ident ..
    $ arcyd fsck
Merge branch 'fix/ignore_ident_attr2' into fix/ignore_ident_attr