* Add shrink option that allow change default shrink
Shrink option allow to scale the godot application. This path enable
dynamic change of this value in the options.
* Fix the computation of cursor location
For an unknown reason the function get_local_mouse_position return
incorrect current_pixel when shrink is not 1. This path compute the
transformation manually and povide correct values for any shrink value.
Added the ability to change grid type in Preferences, and made an isometric cell size value which affects just the size of the cells of the isometric grid. Also updated translations.
Instead of drawing individual lines, execute draw_isometric_tile() multiple times. What this method does is basically draws a single isometric tile, which then gets repeated for the entire canvas size. Also moved all the grid logic to a new script, which gets updated less often that Canvas.gd, for optimization purposes.
Works better than the previous method, although it might be a bit slower, and currently does not work well if the canvas size is not divisible by the grid size. For now, it only gets affected by the grid width. Changing grid height has no effect.
The Canvas is now single node, instead of having multiple canvases for each frame. This should also be a performance optimization, since there are less canvas nodes, so there are less _input() calls. It should also fix a rare Undo/Redo issue with motion drawing and making lines. Could be unstable, needs more testing.
As a side effect, the guides are now the same for all frames, so this should also close #246.
ColorAndToolOptions has now the same code for left and right tool options, with more similar refactoring coming soon to places like Canvas and DrawingAlgos
