v1.7

This is a bugfix release. The major fix relates to joint limits on ball joints but there are a few other tweaks about the place. There is a Windows 64 bit installer, a Windows 64 bit portable version, a Mac Intel version and a Ubuntu version. There is also a Windows command line version (GaitSym2019CL.exe) which is useful if you are using some sort of machine learning to optimise drivers (e.g. with the scipy_optimize.py script).