[WIP/RFC] Drawing simple shapes on the map

[hauke96]

Maybe the PathOverlay helps. I don't know what's possible with OsmDroid and the overlay, maybe some of the following features aren't doable.

Tasks/acceptance criteria:

• In the toolbar should be a button (maybe with a pen or path icon) to enable the drawing mode
• After clicking the draw-button, the toolbar changes and will have the following buttons
  • Note-button to go back to note-mode
  • Line-button to draw lines
  • Polygon-Button to draw polygon
• In draw mode, the following map interaction should be possible
  • Tap on a shape selects it
  • Tap on map adds a new point for the current line shape or starts drawing a new line shape
  • Each point of the selected shape should be able to be moved

Discussion/questions:

• Should there be a color button to choose a color or should drawn shapes also have a category?
• How to modify polygon shapes?
• Should shapes have a text (like "this area is grass" or so)