Fix issue with panels extending outside [zmin, zmax]

[eyoung55]

The mesh generating code should identify and throw a warning or exception if the panels extend below the z_min or z_max walls. OR a special case could be included to identify those panels which are (now) only composed of 5 sides where the 6th is omitted. So a 2D domain might look like:

                top
       _____________________
       |                   |
       |                   |
inflow |       _____       | outflow
       |       |   |       |
       |       |   |       |
       |_______|   |_______|
              bottom

[arswalid]

subroutine added to check that panels are within the domain after rotation application