Merge RF and RFBridge code

[Niek]

Related issue: #1425

This PR merges the RF and RF Bridge code. No changes in configs/defines. I also took the freedom to rename the module to generic "RF".

[mcspr]

I'd suggest to stick to rfbridge.ino as base and keep RFBRIDGE naming when appropriate (per #795 (comment) and general issue of still having either two or one direction rf communication modules)
Plus, it will be much shorter diff.

This does not modify modules behaviour, thus may be safely merged. Later PR can address RFB_DIRECT / RF_SUPPORT, RF_PIN / RFB_PIN etc.

[Niek]

I agree with your comment on the filename and diff size - I updated the PR. I kept the function names (like rfbSetup() etc) the same as well. I definitely think it would be wise to identify this as a generic "RF" module though, also in the debug log. In fact the previous RFBridge code did not register as a module, which is strange.

[mcspr]

lgtm, besides comments
if @xoseperez does not mind rfbridge->rf naming

[Niek]

Thanks a lot, I missed that! PR has been updated now.

[Niek]

Any chance that this can be merged?