Add hard decoder gates (nand, inv, pnan)
Add conditions for routing using LI layer in s8.
Generalize bus layers for decoders.
Move custom cells to own directory.
Fixed via directions, etc.
Add 4x16 hierarchical decoder and test case
Changes to allow decoder height to be a 2x multiple of bitcell height.
Split of control logic tests.
Fixed track spacing in SRAM and channel router
PEP8 cleanup.
Convert to use li layer in pgates.
Fix multifinger devices with li layers.
Simplify wordline driver input routing.
Fix power pin direction option update.
PEP8 cleanup
Changes to simplify metal preferred directions and pitches.
Split of control logic tests.
Convert metalN to mN.
Generalize helper constants in modules for
space, width, enclose, etc.
Use layer stacks whever possible.
Try to remove drc() calls in liu of helper constants.
Moved create_netlist and create_layout to the pgate class
from which everything is derived. Modified all pgates
to have consistent debug output and order of init function.