Branch cleanup

[g-scott-murray]

Now that the repository has been migrated here for future development, I propose the following cleanup:

• The "AGL" branch be renamed to "dunfell" (or a new "dunfell" branch be forked from it). This would better match OE/Yocto community branch layout expectations.
• The "master" branch be renamed to "main" (or potentially "dev", etc.) and the "AGL"/"dunfell" branch changes merged into it, or alternatively the current "master" be replaced with a new "main" branch off of the "AGL"/"dunfell" branch (and the existing "master" deleted). Dropping the "master" naming seems worthwhile to match what the wider FOSS community is moving to, and we need to establish a new baseline for tracking upstream OE/Yocto development (e.g. the syntax override changes in 3.4/honnister).
• All other branches be removed. They all seem not interesting at this point IMO, and if this new location is intended to be a ongoing maintained source, dropping the 5-6 year old experiment/feature branches to avoid clutter seems worthwhile.

[keplersj]

I think all of these changes make a lot of sense. I've made some changes locally to support the Hardknott version of Yocto and would like to get these upstreamed. What would be the best path to getting branches set up in the OpenEmbedded style (a branch for each yocto major release)?

[keplersj]

@jjardon Are you or someone else responsible for this repository?