Ambassador - Provide possibility to disable everything at root level - with corresponding possibility to enable at path/method level

[kylehodgetts]

Add global level disable option to enable blanket disable on all paths and operations. Paths and Operations can then be enabled when they are deemed to be ready by overriding the disabled field at the path and field levels.

Change disabled field in SubOptions from boolean to pointer to a boolean to implement the following semantics:

• If nil, not explicitely set, then check for value at level above - if at operation, check path level. If at path level, check global level
• If has a value be it True or False, disregard the disabled setting at the level above as it has been explicitely set

Implement useful helper methods IsOperationDisabled and IsPathDisabled with the Option struct reciever which implement the semantics listed above

resolves #148

Checklist

• [ ] tested locally
• [ ] added new dependencies
• [ ] updated the docs
• [ ] added a test