Reorganize repo

[Clonkk]

• Reorganize repo to separate bindings from higher level nim specific API
• Add check for len > 0 in send before copyMem
• Add [] and events() and len() for poller to simplify polling code (having to manually deal with bitops is poor IMO)
• Add destructor for TConnection
  • Add ownctx field to TConnection to know wether or not the connexion own the context
  • destructor added behind a when defined(gcDestructors), close PSocket and owned PContext
  • Add sockaddr that keep in memory the address of the TConnection
  • Useful because disconnect, unbind proc somehow needs the address

The only API change is adding 2 fields to the type TConnection. No proc changed signature - just more proc added to improve the quality of life.

@Araq (or any maintainer that read this) at your leisure, I'd like have your opinion on the change before I spend any more time on this.

[Araq]

I would go even further in the reorganization:

• Remove the outdated T/P type prefixes.
• Add CI integration.
• Bump version to 1.0.

[Clonkk]

Which CI is available (Azure or Travis I assume) ? Is there a yaml template to follow ?

[Clonkk]

@Araq I think this PR is ready for review.

Since we went for a 1.0 :

• I renamed obsolete type to ZTypeName (prefix to avoid name conflict)
• Renamed field with 1 letter name to a more explicit context, socket
• Added rudimentary tests (no auth features tested)

I used github actions based on https://github.com/iffy/install-nim. If that's not the preferred way for CI, I'd be happy to change it to whatever is standard for "official" repository. The github actions simply uses testament to run the tests and examples.

There is no documentation generation for now as I'm not sure how you want to handle it for this repo (I usually use github pages on docs/ folder and commit the generated files).