restui 8.x-1.14

#2869443: REST UI has been creating 'method' granularity configuration: provide update path to automatically convert to 'resource' granularity where possible by Wim Leers
#2868690: restui.permissions.yml conflicts with rest.permissions.yml by Wim Leers
#2831716: REST UI does not support "resource" granularity by Wim Leers, rogierbom, gvso, clemens.tolboom, juampynr, pasive
#2851126: The UI says "disable", but it's really "delete" by Wim Leers
#2868729: Delete composer.json — since the d.o composer facade, it's unnecessary by Wim Leers
#2868728: REST UI docs claim you need HAL to create content, which hasn't been true for years by Wim Leers
#2303369: Until #2300677 is fixed, show in REST UI that config entity resources are read-only by clemens.tolboom, Wim Leers, andypost, Berdir
#2851127: REST UI module should not be rebuilding routes by Wim Leers, rogierbom
Convert UI test into a BrowserTest (plus fix a bug)
#2744445: Clean-up codebase according current code standards by andypost
Add .gitignore