requires https://github.com/TryGhost/Ghost/pull/8093
- adds `theme.activate()` method and associated adapter method for activating themes rather than relying on `settings.activeTheme`
- minor refactors to the `modals/upload-theme` component to use a full theme model
refs https://github.com/TryGhost/Ghost-Admin/pull/210
- removes unused `activeTheme` property on `gh-theme-table`
- updates label generation in `gh-theme-table` to add folder names when there are duplicate package.json name+version combos