Copter: Throw mode check altitude params

[JanMaciuk]

Allow the user to set altitude restrictions in which a throw can be detected via parameters.
This feature has been really useful preventing accidental throw detection, which I am sure many users struggled with during fully autonomous missions.
The scenario in which we use it is with a VTOL plane which has many copters attached to it.
The copters would tend to detect a throw and attempt to stabilize when still attached to the plane, during transition to fixed wing or turbulence.
The problem is solved by simply setting the throw altitude max parameter below the transition altitude.
Only when the plane descends to perform the drop copters are able to stabilize.
Code modifications are very simple, testing was performed in SITL to ensure the feature works as intended with different parameter values.
This is the second version after all reviews, we used these changes for dropping copters from an autonomous plane in designated altitude range.

[rmackay9]

LGTM, thanks!

[rmackay9]

Merged, thanks!