Add Behavior support to Defined Interfaces and Defined Entity Types

[adambarreiro]

Overview

This PR serves as the foundations of vmware/terraform-provider-vcd#1074
It adds methods to both Defined Interface and Defined Entity Type types to manage Behaviors and Behavior Access Controls.

Context

Behaviors are explained here, but in simplified words, they're "procedures" that belong to RDE Interfaces, are inherited by the RDE Types that use those Interfaces and are invoked on the RDEs that instantiate those types.

Also, Behaviors can be overridden at the RDE Type level. For example, if you use a RDE Interface with behavior "A", you can override what it does in a Type that uses it.

Also, Behaviors have "Access Levels", which can define what operations can be done in that behavior.

[Didainius]

A few inline questions. Lots of boilerplate - which is sort of a good thing :)

[Didainius]

Just a few queries as this is a lot of boilerplate. Will have to think in future on how to reduce code for standardized endpoints like these.

[lvirbalas]

I found it confusing to see "override" being used as a noun and as a verb in the same scope. (It's hard to tell whether it's a noun or verb in English with little context). So, I have added a suggestion to use a noun through out.

[lvirbalas]

Thank you for the adjustment!

[Didainius]

rde tests passed