Improve XBAR Documentation and Examples

[r0oland]

While working on the XBAR on my RT1064, I noticed that all aspects of that feature are severely lacking compared to many other "peripherals" of the 1064 (and most other iMX chips I assume).

The documentation is scattered trough different parts of the manual, there is no application note providing a concise example, the MCUXpresso IDE does not support the peripheral and the provided examples are very specific and overly complicated to get started.