verilog2def should coerce area to multiples of core site

[tajayi]

Priority: Medium

Tool: verilog2def

Version: 98568f2

Issue:
The track information generated by verilog2def includes an offset (derived from tracks.info) that defines the routing grid for TritonRoute. It is critical that these are correct for proper routing. The offset is related to the design size (core_area and die_area) and must be aligned.
A simple way to avoid a pitfall is to ensure that the core_area and die_area coordinates snap to the placement tile. This can be found in the site section of the lef file

Steps to reproduce
Run verilog2def on any design. The nangate45 platform is more prone to misalignment due to the size of the site. The grid is most easily observed using a viewer such as innovus