new feature: Draw Polygon with GPS point in Mission Planner Android

I need new function, to get TABLE/CELL GPS position to mark new polygon point. I now the FOLLOW ME and MOVING BASE extra function (test page) have a create new icon in GPS position, I propose create a new item in DRAW POLYGON function “CREATE GPS POLYGON POINT” (if have a better name, no problem), this function will create one new polygon point using internal GPS position. This option will be enabled only have a actived FOLLOW ME or MOVIND BASE, because the external GPS was selected before.

I like to do that, but I am old deveper and I don’t compile to Android.

Thank you can do it ! I feel this will be very interesting who need mark polygon using same Android Table/phone !!!

#### Version
_What version was the issue encountered with_

#### Platform
[ x ] All
[ ] AntennaTracker
[ x ] Copter
[ x ] Plane
[ x ] Rover
[x ] Sub

#### Airframe type
all

#### Hardware type
Android devices

Start by locating the Android DRAW POLYGON flow and the existing FOLLOW ME and MOVING BASE GPS-position actions. Trace how the active internal or external GPS source is selected, then define the new polygon-point action and verify it is available only with FOLLOW ME or MOVING BASE active and adds the current device position.

Written by the indexing model from the issue text.