Parameter xml metadata in .px4

I'm putting this up here for discussion. I would like to discuss the option of having the parameter xml metadata file be part of the .px4 file. This way QGroundControl can get the metadata to help build a better UI for parameter ui. This will allow for help for each parameter directly in QGC as well a range/value validation. By putting it in the .px4 file each time firmware is updated new parameter metadata is updated as well.

As part of this change (not yet coded) i think that the parameters should be versioned as well. Both in the parameter file as well as having a parameter itself that contain the parameter version. The contract would be that bumping the parameter version means that older version parameter sets would no longer be valid. This will prevent issues like saving a set of parameters as a file in QGC and then loading them over newer firmware that is incompatible with that set of params.