BILS updater fixes galore

I built on Robert's safeguard, and added some of my own. :)

1. Added comments like crazy. This was an early script of mine, and my
management skills were lacking. I cleaned up some comments and made them
prettier.
2. Replaced several old "= 0" or "= 1" with cancel/checked global
variables. Makes it easier to visualize with what we're working.
3. Replaced several lines of code throughout with new FUNCTIONS FILE
functionality. Big one there would be the date filling issue, which came
from single digit months in budgets starting with a double digit.
Computer would declare as single digit, even when starting with double,
but if the user started with a double digit iteration of a single digit
month (user added their own 0), it'd work. create_MAXIS_friendly_date,
like the mighty honey badger, don't care 'bout this, and works better
here with less lines o'code. Tested it a dozen times, and it's working.
4. Building on Robert's do...loop, I added a check for users NOT filling
in the BILS ver dropdown. BILS requires it, and will freak out if it
isn't there. Now it is.
5. Got rid of those pesky "/////"s when you're using a case without a
budget. Just told the budget_begin and _end to replace a trimmed version
of itself, instead of the default.

Hopefully this solves the problem and I can go back to avoiding my BILS
(see what I did there?). :)