Change ?version url parameter values so they are more explicit.

[simonredfern]

We should specificy the standard e.g. OBP, BG or UK in the url parameter.

OBP

https://apiexplorersandbox.openbankproject.com/?version=3.1.0 -> ?version=OBPv3.1.0

Berlin Group

https://apiexplorersandbox.openbankproject.com/?version=v1 -> ?version=BGv1

UK

https://apiexplorersandbox.openbankproject.com/?version=v2.0 -> ?version=UKv2.0

When this tickets is done we should look at the parameter values sent to the resource docs endpoint and make more explicit whilst maintainting compatibility.

[constantine2nd]

@simonredfern Ready for testing.