HVAC Systems Updates

Fixed several bugs during updates.  Added System Type 2 and 4, and a
single speed DX heating coil.  System Type 2 and 4 still need testing.
One Speed DX Heating Coil additions

WIP, now PTHP 2 has the ability to override parts of the DX heating coil
for single speed.  Still have to add two speed and plenty of error
checking.