existing PUT endpoint updates oauth app meta data (#2585)
existing PUT endpoint updates oauth app meta data (#2585)

added changes for https://github.com/TykTechnologies/tyk-analytics/issues/1432

please note that endpoint was already there but updating oauth metadata was disabled (so this PR enables it).

this also requires updating docs because existing PUT-endpoint is missing there 
lonelycode/tyk,lonelycode/tyk,lonelycode/tyk