the variable CAM_P_G has the same prefix as the CAM_P group. We want
to allow for parameters having a common prefix with a group, so we
need to keep searching after we've found a group that matches the
prefix
We would like to be able to use Vector3f as a parameter while exposing
the individual elements of the vector as MAVLink parameters. This
change to AP_Param makes that possible, by giving AP_Vector3f a dual
personality
adding a idx element to the GroupInfo will make it less likely that a
developer will change the IDs of group elements, and make it easier to
see that these IDs are important for identifying a variable in EEPROM
The header packing has changed to make it 24 bits on all platforms,
which allows us to lower the EEPROM variable max size to 1024 bytes
again