Declare mapping of resource ID to resource key in the config file

[jcos1]

Adding a way to declare mapping (per client) of resource ID to resource key in the config file of the router.

For those cases where you know which client(s) will connect and which keys they will be sending.

Advantages:

• Avoid the overhead of the declare frames
• No strings needed in the client (every byte counts)
• Faster restart of the communication after an interrupt

Disadvantages:

• None ??