Support for KX1 FPGA module

[MarcoVogt]

This PR implements changes to support the Enclustra Mercury KX1 FPGA module.

• New xdc constraint file for the pinout of KX1. The 160 and the 325 version use the same constraint file.
• The tcl build script was modified to parse the required build options directly from the unique xdc file name. The 'output product' file names (.bit, .msc) are also generated from these parameters. An optional 'suffix' parameter can used to further modify the file names.

[cbespin]

Looks good to me, I will merge this. Thanks!