Use a struct for the OOK configuration and add frequency tuning

[docprofsky]

Use a struct store the configuration information for the OOK app. This adds the frequency to the configuration so that devices on different frequencies can be controlled.

Additionally, some minor cleaning up of the code is done.

[travisgoodspeed]

I like that this adds some legibility to the OOK configuration, and also that it supports cleanly mixing OOK signals that are on different frequencies or at different rates. The additional consumption of code memory shouldn't be much of a problem.

Any volunteers to review this PR?