add up-front version checks for 2.7 to executables

Summary:
The code base currently depends on version 2.7 of Python, any earlier
than that and it won't have the requisite argparse feaures.  Any later
than that (3.x) and there are breaking changes in the syntax.

Prevent nasty runtime surprises by enforcing version 2.7 as early as
possible.

    The version check itself will not work prior to Python version 2.0,
    that's when sys.version_info was introduced.

Test Plan:
Changed version requirement to earlier and later to ensure that it
fails both ways.

Reviewers: oparanal

Reviewed By: oparanal

CC: phab

Differential Revision: https://sibld.phab.dev.bloomberg.com/D139
phlsys_dictutil: add 'set_if_true' convenience fn

To simplify code like this:

>>> d = {}
>>> if thingy:
...   d['blah'] = thingy

You can do this instead:

>>> set_if_true(d, 'blah', thingy)

Test Plan: added doctest, $ ./precommit.sh
Adding a notice about the use of anonymous users

Summary:
Added a notice about use of anonymnous user account for mysql in
the default.pp manifest.

Test Plan:
Make sure markdown appears as intended on a mark down
editor/viewer

Reviewers: jevripio

Reviewed By: jevripio

CC: phab

Differential Revision: https://sibld.phab.dev.bloomberg.com/D141
Refactor aoncmd_query.process, split out functions

This function has grown too complex, split it out into separate
functions to reduce complexity.

Test Plan:
$ ./precommit.sh
testbed/arcyon $ ./exercise_arcyon.sh
various scripts in /examples/arcyon
phlsys_timedeltatostr: more helpers

Add helpers for returning string representations of durations as days,
weeks, months etc.

Include usage examples as doctests.

Test Plan:
$ ./precommit.sh
Arcyon query: more time / date formats in results

Add these new formats to the results objects:
    humanTimeSinceDate
    daysSinceDate
    weeksSinceDate
    monthsSinceDate
    humanDateModified
    humanDateCreated

Update examples/arcyon to take advantage of the new data.

Test Plan:
$ ./precommit.sh
Various in examples/arcyon