Strong default grids

Right now, the default grids can be specified per default or per technology.

However, this only populates the "View/Grids" menu, but does not enforce a certain grid.

The proposal is to allow specification of a strong default grid, e.g.

```
0.01!,0.02,0.05
```

The exclamation mark indicates to set 0.01 as the grid, except if one the of the grids is selected.

