SWU: Better resilience against overwriting of update configs
SWU: Better resilience against overwriting of update configs

Don't allow overwriting of "octoprint" config through plugins, don't
allow overwriting of already registered configs unless id to register
matches plugin identifier (in which case the already registered config
was probably a case of a copy-paste-error from another plugin).

foosel/OctoPrint,beeverycreative/BEEweb,Jaesin/OctoPrint,bicephale/OctoPrint,beeverycreative/BEEweb,beeverycreative/BEEweb,bicephale/OctoPrint,bicephale/OctoPrint,Salandora/OctoPrint,Salandora/OctoPrint,Jaesin/OctoPrint,Salandora/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint,JackGavin13/octoprint-test-not-finished,Salandora/OctoPrint,foosel/OctoPrint,JackGavin13/octoprint-test-not-finished,JackGavin13/octoprint-test-not-finished,Jaesin/OctoPrint,JackGavin13/octoprint-test-not-finished,beeverycreative/BEEweb,bicephale/OctoPrint,foosel/OctoPrint