Add support for json schema draft 4, 6 and 7

[rajpra8]

I saw that comment that because of lack of community support, newer version of json schema is not going to get supported.
While going through latest specs, I noticed few breaking changes but I was able to make small tweaks to at least to get the schema written in version 7 be parsed by the code.
Let me know if there is any work already in progress to add support for newer versions. I would love to join the effort.

[cowtowncoder]

@rajpra8 I am not aware of efforts: you would be welcome to start making improvements for sure. Probably the best place to ask for others interested in helping would be jackson-dev list:

https://groups.google.com/g/jackson-dev

Adding some level of support for newer versions sounds useful!

[rajpra8]

Thanks @cowtowncoder. I have joined the group has posted my initial message. If I don't get any response, I will start a fork and start working on adding the support for versions of spec.

[KannarFr]

@rajpra8 any news?