Trello cli for server team boards (POC)

[Bryce Harrington]

I've added a few scripts to ubuntu-helpers to interact with our trello
boards from the command line:

### Daily Ubuntu Server ###

$ usdaily list
TODO:
* Write git-ubuntu merge test cases
* MP page filtering out the semi-done cases

Doing:
* LP: #1583705 logwatch / postfix
...


### Groovy Merges Schedule ###

$ usmerges list
Groovy Merges Schedule:
* 20.05:
  - dovecot
  - spamassassin
  - postfix
* 20.06:
  - nginx
...


### Proposed Migration ###

$ usmigration list
Languishing:
* linux-meta-oem-5.6
* linux-meta-oracle
* linux-oem-5.6
...

TODO:
* dbus-python
* pygobject
* rgain3
...


### SRU ###

$ sru-board list
Languishing:
* intel-microcode
* libappindicator
* stress-ng

To Do:
* rpi-eeprom
* iproute2
* apache2
...


The scripts are basically just wrappers around `so-trello`.  You'll need
to install so-trello via the snap, authenticate, and make
a ~/.config/uscards.conf (see uscard's README).

Code is here:

    https://code.launchpad.net/~ubuntu-server/ubuntu-helpers/+git/ubuntu-helpers/


You may remember I was doing some experimentation with so-trello earlier
this year.  Since "trello cli" came up more than a couple times in
recent standup meetings, I dusted it off and got them minimally
functional.  This is super proof-of-concept, and I'll likely adjust
behavior and formatting a bit before I consider them done.

Next steps are to add a few more commands ('add', 'finish', 'comment',
'review'), and ability to filter listings by tag or username.  Meanwhile
I'd like to get feedback on if this looks useful and if there's specific
functionality others would like to see.  Patches welcome too, of course.

Bryce