Pure Julia WKT2 to PROJJSON conversion

[Omar-Elrefaei]

Working towards #150

[juliohm]

@Omar-Elrefaei this looks promising. Please let me know when it is ready for review.

[nsajko]

Some deep issues with the design here:

• Calling Meta.parse on the WKT string can't be correct and is obviously a huge hack, no offence. It's parsing foreign code as Julia code!
  • In particular WKT strings have completely different escaping than Julia strings, the former escape by repeating the double quotes, while the latter escape with backslashes.
  • It could also perhaps be considered a security vulnerability, unless the WKT strings are completely vetted upfront on each update of the EPSG data base.
• WKT keywords are case-insensitive, furthermore in some cases several alternative names are possible for the same keyword, so hardcoding the names like here can't be correct.

My design is more complex in part because it tackles these issues and more.

[juliohm]

Thank you for sharing @nsajko. Appreciate your inputs.

If you can evolve your PR to a final version to show the technical advantages in practice, we will happily consider it.

Both PRs are still work in progress, but it is really nice to see the high quality of the attempts already.

[Omar-Elrefaei]

I think this is functionally mostly there, save for few rare edge cases.
The code itself would take another round of cleanup tho, especially the comments.

few of the concerns brought up by nsajko are justifies, some are design tradeoffs, and some are a non-issue, I think. I'll take time to elaborate soon.