Add code export of the 'storeJson' command

[NikkTod]

🚀 Feature Proposal

As data driven testing is a good edition to the new Selenium IDE, it will be helpful if users are also able to export the 'storeJson' command.
Currenly, when we try to export a testcase that cointains the 'storeJson' command to any of the available languages , we get the exception:

throw new System.Exception("The storeJson command is not yet implemented for this language.");

Motivation

Coding this command behaivior can be difficult to a junior.

[toddtarsi]

@NikkTod - I hate when we have commands we don't export. I'll try and look into this a couple weekends from now. Hopefully it won't be too bad.