Document how to remove a mower

[Jeff Winn]

Is your feature request related to a problem? Please describe:
Related to #232 i had to remove the cached accessory last night to get the issue to clear up when I deployed the plug-in. There is no documentation how to remove plugins from the accessory cache.

Describe the solution you'd like:
I need to add documentation to the website detailing how to remove an existing mower from the accessory cache.

Describe alternatives you've considered:
Not producing the documentation, it’s pretty straight forward but people may not know it’s there.

Additional context:
Probably needs to go on the website under extras. It’s likely going to be used more and more as people update iOS to the newer version.

The documentation should also indicate the removal will also break any scenes or automation setup against the device and will need to be reconfigured.