polymake-json conversion

[apaffenholz]

a direct conversion from polymake to json and back requires upgrade scripts for the json format between different polymake versions

current xsl upgrade scripts apply to the xml before the data is intepreted in polymake

[apaffenholz]

some more open things:

• conversion json to polymake
• handling of attachments
  -handling of extensions

We could avoid type detection by pattern matching if we supply a to_JSON method to all c++-Objects.

[apaffenholz]

Proposal for a "quick fix":
The db stores the xml of the polytope alongside the json conversion.

Then it would suffice to have a conversion from polymake into json to be able to store a polytope in the db. For retrieval we use the stored xml. This also removes the versioning problem, we just send the xml through the existing scripts. In this case even a partial conversion suffices, only storing the properties we actually use as an index.
If at some point we have a full conversion in both directions we can switch the retrieval method and remove the stored xml from the db.

The con is storage: we double the required space.
?