closes#5850
- filters were added so that apps could change the output of the helpers, but as async helpers are a hack, this led to issues
- apps aren't currently a working part of Ghost, so for now, lets remove the filters
- we'll add these back when we have a better implementation of async helpers & this style of app is back on the cards
no issue
- Split theme helpers into individual files for each
- Do the same for tests
- Have utils to share some things between them
- Move assetHash onto config