[#22205, #22206, #8947] Adapt agov_zen to provide only minimal colouring
(grayscale) and be suitable for sub-themeing (no imported fonts et al)
[#22205, #22206] Add aGov Barton sub-theme to provide original colour
scheme compatibility
[#22205, #22206] Add aGov STARTERKIT for building agov_zen sub themes.
[#22206, #22207] Ensure aGov Barton is enabled by default on install
Revert update to features 7.x-2.0
Don't hard-code the default theme
Merge branch '7.x-2.x' into 22205-22206-subtheming-for-agov_zen

Conflicts:
	modules/custom/agov_core/agov_core.module
	themes/agov_zen/css/agov_styles.css
Merge branch '7.x-2.x' into 22205-22206-subtheming-for-agov_zen

Conflicts:
	themes/agov_zen/css/agov_styles.css
	themes/agov_zen/sass/_colors.scss
	themes/agov_zen/sass/_forms.scss
	themes/agov_zen/sass/_layout.scss
#22206, #11337, #11365: Rebase sub-theming branch against current master and resolve conflicts. Fix dependent issues.
Logo has changed, so alt logo must be specified for installer... also gives us a maintenance page...
Update composer reps
Add missing current page visibility setting for crumbs
Merge branch '7.x-2.x' into 22205-22206-subtheming-for-agov_zen
[#22206] Fix an issue where field sets in the installer had unreadable labels
22206: Removed extra .ruby-version files
Merge branch '22205-22206-subtheming-for-agov_zen' of github.com:previousnext/agov into 22205-22206-subtheming-for-agov_zen
22206: Removed line comments from themes and extra styles from AGOV_STARTERKIT
Merge pull request #252 from previousnext/22206--removed-line-comments

22206: Removed line comments from themes and extra styles from AGOV_STARTERKIT
22206: Removed placeholder files from barton theme
Merge pull request #253 from previousnext/22206-removed-placeholder-barton-files

22206: Removed placeholder files from barton theme