Add another way to describe and match prisms

[petrvanekrobe]

In some cases it is not possible to know the exact prism dimensions, or perhaps the console doesn't care about exact details but is happy to know the general shape and facet count for fixture exchange.

For this, add a list of known prisms which can be assigned to the prism, to allow simpler fixture matching.

TODO: add predefined prisms list here to better support this issue.