Add -gridify

[simonepri]

Command description

Given a large Polygon or MultiPolygon split it into squares.

Example

Transform this: into something like this:

How to do this without a new command

• generate a grid of rectangles.
• clip from the grid the original polygon.

[mbloch]

I propose simply adding a command for creating polygon grids (-polygon-grid), which have a number of applications. In addition to rectangular grids, it would have options for creating hex grids and triangular grids. Once you have a polygon grid, it only takes one -clip command to accomplish the "gridify" effect -- I'd rather not add a special-purpose command for that.