Make BTE API more generic

[Zarithya]

This PR moves code specific to Wiimotes fully into WPAD and adds the functions BTE_InquiryEx and BTE_PeriodicInquiryEx, which allow the user to specify a LAP they wish to use. This will allow other code to use the Bluetooth adapter for things which aren't Wiimotes more easily (should hopefully address #230 ).

Also I found a bug with one of my third party Wiimotes causing a null pointer deref so that's fixed here too.