Possible known bugs

[nmsutton]

A search of grep -iRc 'FIXME' ./ in the ./carlsim directory (source code) shows 92 mentions of the comment "FIXME" in source code files. It could be investigated if these are known bugs in the code. Issues for known bugs could be posted in Github. In terms of open issues, there are 13 in CARLsim3, 22 in CARLsim4, and 9 in CARLsim5. Given that CARLsim6 is the only version actively supported, consolidating prior issues into a single issue list would be helpful. Even if issues are unable to be fixed in a near time period, noting that they exist in the user guide/docs can help users at least be aware of known issues.