Misc bug fixes & enhancements.

[samoliverowens]

• Make it possible to specify an initial facet temperature in namoptions.

• Enable more than 3 wall layers (this is currently hard-coded in initfac and modEB).

• Output facet dT/dz as well as T.

• Remove upwards-oriented facets in buildings consisting of stacks of blocks.

• Vertically flip topo & topomask.

[samoliverowens]

* Allow blocks on the edge of the domain when using the energy balance.

@bss116 I realise I should actually discuss this first - the preprocessing currently doesn't allow facets to sit right on the domain edge when using the energy balance, because it causes problems when calculating view factors between them and the bounding walls. My instinct was to just remove this facets on the edge, because I was working with staggered cubes, and it actually makes some sense in this case because then the half-block on one side of the domain is actually touching the one on the other side due to the periodicity in y.

I was worried about what would happen in other cases, but maybe the ibm might not even 'notice' the missing facets, because it operates on blocks? Let me know what you think about effectively permitting blocks with a side missing, at the moment I think I'll just keep this in my branch.

[bss116]

Hm I don't know. I think you might be right that it is okay for the IBM, I think there the grid cells get the "block" properties, and the facets (i.e. block walls) are only relevant for the boundary conditions (and a flux into a block does not do anything). But I'm really not sure about this, you'd need to check this carefully before changing. If your only concern is the staggered grid, why not just moving the boxes a bit so you don't split them up at all?