v14.09 with formula enhancements and component updates

Major Enhancements

1. Update Imageflow #2880
2. Remove dependency on Newtonsoft Json - use System.Text.Json instead (note we tested this extensively, but this is the riskiest update)
3. Add json schema to editing image-resize recipes #2873
4. Improve registration UI #2881
5. Advanced control which folders to exclude on app-export using App_Data/app.json #2854
6. Removed Newtonsoft and replaced it with System.Text.Json #2916

API Formula Enhancements

1. Add user information isContentAdmin, email, guid, name, username #2843 #2882 #2877
2. Improve CmsContext.User to also have Email, Guid, Name, Username #2883

Bugfixes

1. Creating list items creates more than one item #2869
2. Hitting + on content-list with no items and then saving many times with ctrl+s added it many times #2872
3. Hitting + on a content-list with no items previously simulated edit, now it adds it after the first demo-item #2846
4. On first load the app or content installer show warning #2864

Other

1. Replace moment.js with day.js #2863
2. Remove dependency on material icons loaded from CDN #2868
3. Internal APIs to have IsSiteAdmin, IsSystemAdmin, IsContentAdmin #2876

Full Changelog: v14.08.00...v14.09.00