Provide Ardupilot parameters fetching/updating routes on dedicated service or in Mavlink2Rest

Right now one needs to request Ardupilot to update the parameters list, watch for PARAM_VALUE messages, parse than (veeery cumbersome) and store somewhere, as well as watch for changes. Updating them is a whole other thing.

Right now both BlueOS and Cockpit already implement it, in a duplicated fashion, and any other extension that wants to deal with Ardupilot Parameters will have to do the same.

My suggestion is that we abstract this whole process to simple REST endpoints (e.g.: `/fetch_current_parameters` and `/update_parameter{id}`) inside a dedicated service or in Mavlink2Rest itself.