closes#8056🎨 Collect together the package-related utils
- read directory actually reads a directory of packages
- parse package json is very tighly related to this
🎨 Move filterPaths -> packages.filterPackages
- this function is related to packages, not settings
- move the function to the new utils/packages
- add 100% test coverage
🎨 Simplify filterPackages code
🎨 Simplify reading of packages & themes
- This massively reduces all the complex code in the read packages & themes utils
- Added full test coverage
🎨 Improve & clarify active prop in filterPackages
- active is returned from API endpoints to combine data from multiple sources
- see https://github.com/TryGhost/Ghost/pull/8064#discussion_r103514810🎨 Better error handling
🔥 Temporarily remove custom error templates
- we will reimplement this later when we have got a better concept of loading the active theme in place
- refs #8079
refs #5940, #5923
- make read-directory ignore invalid package.json files
- display a warning about invalid package.json files on startup
- add tests to ensure read-directory continues, even with invalid package.json files
closes#5492
- remove core/server/require-tree.js and split it into modules
- add read-directory module to recursively read directories
- add validate-themes module to scan themes and return errors/warnings
- add parse-package-json module to parse json and validate requirements
- rewrite core/server/models/index.js to manually require models
