Kiva cell/vertex connectivity arrays.

c +++ kiva-3 notation: i4 refers both to vertex #4 and the cell shown:
c +++
c +++
c +++                         7/--------/|6
c +++                         /        / |
c +++                        / |      /  |
c +++                       /        /   |
c +++                     8/--------/5   |
c +++                      |   |    |    |
c +++                      |        |    |
c +++                      |  3|-  -| -  |2
c +++                      |   /    |   /
c +++                      |        |  /
c +++                      | /      | /
c +++                      |        |/
c +++                     4----------1
c +++                                     top=i8tab(i4)
c +++                                          |
c +++                                          |   derriere=i3tab(i4)
c +++                                          |  /
c +++                                          | /
c +++                                          |/
c +++                  left=imtab(i4)--------<i4>-----right=i1tab(i4)
c +++                                         /|
c +++                                        / |
c +++                                       /  |
c +++                        front=jmtab(i4)   |
c +++                                          |
c +++                                   bottom=kmtab(i4)
c
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cell 'i4' is connected to vertex 'i4'.
To get the points of cell 'i' is thus done in the following way:

i
i1tab(i)
i3tab(i1tab(i))
i3tab(i)
i8tab(i)
i1tab(i8tab(i))
i3tab(i1tab(i8tab(i)))
i3tab(i8tab(i))

Only three of the faces have boundary condition. They are stored in the following arrays

bcl - boundary condition left face
bcf - boundary condition front face
bcb - boundary condition bottom face

To get the other boundary conditions, you must get the neighbouring cells
and obtain the bc from them.

The bc values are:
1.0  - moving  - moving (piston top)
2.0  - solid   - solid (wall)
3.0  - axis    - center axis, line
4.0  - fluid   - fluid (i.e. no bc)
5.0  - periodf - front periodic bc
6.0  - periodd - back periodic bc
7.0  - inflow  - inflow
8.0  - outflow - outflow
9.0  - presin  - pressure inflow
10.0 - presout - pressure outflow

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fv - flag for vertices

The values are:

0.0 - inactive vertex
1.0 - flfluid - interior (fluid) vertex
2.0 - flface  - vertex on a moving surface (piston/valve)
3.0 - flbowl  - vertex within the piston bowl
4.0 - flsqsh  - vertex in squish region and above piston
5.0 - fldome  - vertex within head, but not on the surface itself
6.0 - flhead  - vertex on the head surface

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f - flag for cells

The values are:

0.0 - inactive (ghost) cell
1.0 - active cell

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idface - vertex flag for moving surface

The values are:

-1 - Not on a moving surface
 0 - Piston top
 1..6 - Valve nr.

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idreg - cell region number.

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The first non-ghost cell will be '