Use of "ca." in Date section

[jcowey]

This is also an HGV date issue.

Under "precision" one can use the choice "ca." in conjunction with century. This is not desired and should not be possible.

One gets in HGV Format "ca. VI". The underlying XML is correct.

[Edelweiss]

in issue branch and in development branch
https://github.com/DCLP/sosol/commits/issue339