Grid for floor plan upload

[resah]

Description

A grid is initialized together with the map itself, but hidden. When opening the floor plan upload dialog, the grid becomes visible and will be hidden once the dialog closes.

I also had to adjust the icon dimensions to keep the sizes realistic. Since all icon SVGs have some offset in their path definitions, I tried to work around this with expanding the icon in the map (x1.3)

Implements: #14

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