Improve ZDA to Implemented Capability interface

[pwood]

At current capabilities must handle the locking and all other concerns of the ZDA implementation. This means we see a lot of duplication of code, exposure to complex ZCL interfaces (which require node level attributes) - and lots of posibilities for incorrect locking behaviour.

The aim is to refactor the interface between ZDA and Capabilties so that:

• Capabilities do not need to be concerned about ZDA locking.
  • This means structures passed into the capability must be copies.
• Wrap calls to ZCL, so they just take the device object the capability was provided.
  • Means that access to SupportsAPSAck, the transaction sequence are hidden.
• Capabilities store their own data.
• Capabilities can obtain other capabilities from the ZDA (i.e. can get HasProductInformation if needed).
• Poller moves to a per device level.

[pwood]

On the remote chance anyone sees this, this is in the capability_refactor branch at current.