Task titles do not allow colons

[danfinlay]

I just ran into this today, spent a little time tracking it down. At the very least putting this out there to help others find what might be their problem.

[ben-ng]

Pretty sure we cant remove this because so much depends on it, but we could do better to document it and throw a meaningful error if someone does try to use a colon.

[danfinlay]

Yeah, I think an informative error would be good enough, could just run a check before applying the string to whatever can't have a colon.

[mde]

A nicer longer-term fix might be to allow escaped colons, and only using non-escaped ones as the namespace delimiter.