[WIP] Add support for Child Themes
This PR adds support for a theme to extend another theme via a parent: [themeName] directive in the theme.yaml. This PR also supports the theme.yaml being added as a DbDatasource content meaning that an extending theme can be purely driven by the DB.
Storm PR: https://github.com/wintercms/storm/pull/123
@jaxwilko Do we want this PR for 1.2.1 since it's still a draft?
@mjauvin still got some bugs that need to be fixed before it's ready for review :)
So it's mostly done, just has a few glitches?
@mjauvin this functionality is needed for our project that we're launching in November so what release it's tagged for doesn't really matter since it'll be merged when it's ready. Don't consider it blocking against 1.2.1 though.