Add more apps to the ERPNext App Installer

[felix]

ERPNext is a monolith - that means everything is merged into core rather than being maintained as separate apps. There was discussion about there here.

[v7] Update - Schools is merging in ERPNext

Dear all, We are also merging the schools project (GitHub - frappe/schools: Merged with frappe/erpnext - this repo is deprecated) in ERPNext. Schools will now be a module in ERPNext Our goal is make ERPNext inclusive of all domains (monolith). The advantage is that the new user will find it very easy to setup any domain and it will not lead to fragmentation (multiple service providers doing the same thing). As we go ahead, we plan to aggressively merge other domains in ERPNext too. Let us k…