Update bind existing service instance to application process

[richard-cox]

• currently binding an existing service instance to an application process is confusing
• the decision to either create a new instance or bind to existing one is made right at the end of the flow
• this late choice is enough to put of user of going through flow
• the visibility of the choice is also sometimes shown, sometimes not (given existence of applicable service). We might want to reconsider this, though only after changes above

[gberche-orange]

Additionally the application page has a tab called "services" (see screenshot1) which

• really lists "service bindings" and not "service instances": should be renamed into "service bindings"

• does not display the service binding name. In table view columns should be renamed "service instance name" and a new "service binding name" column should be added. This is available in v2 binding API and v3.

• has a plus button which offers to create a service instance, instead of a "service binding" associated to the current app: see screenshot2 and screenshot3