[chirp_users] New Daily Build

[Build System]

Greetings,

A new daily build of CHIRP is available.  This includes changes made
directly to the tree yesterday, and may include additional features,
bug fixes, and/or bugs.  If you are interested in trying it, grab it
from the following location:

  http://trac.chirp.danplanet.com/chirp_daily/daily-20210826


A list of the changes included in this build (since the last daily)
follows:

Changes for Build #660
[Jim Unroe <rock.unroe at gmail.com>] [RT22S] add 6.25 and 12.5 tuning steps

The Radtel T18 and Retevis RT22S radios both support 6.25 and 12.5 steps. The
radtel_t18.py driver does not have a "rf.valid_tuning_steps" entry in
get_features() so the COMMON_TUNING_STEPS list in chirp_common, which does not
include the 6.25 and 12.5 steps, is used by default.

This patch adds an "rf.valid_tuning_steps" entry to get_features() and
specifies the TUNING_STEPS list in chirp_common, which does include the 6.25
and 12.5 steps.

Fixes #9305

[Jim Unroe <rock.unroe at gmail.com>] Driver Maintenance: radtel_t18.py

1. Add to PEP8 manifest
2. Perform PEP8 cleanup

Preperaton for #9305

[Dan Smith <dsmith at danplanet.com>] Fix dangling references to generic_xml

A too-swift removal of the generic_xml module on my part left
some dangling references to it in the UI that prevented anything
from working. This removes those and fixes that problem.

Closes #9307