Patch implementation using pure PL/pgSQL

[mysticmind]

The following are changes included:

• Patch implementation using PL/pgSQL plus unit tests, fixes Optimized Patch operations *after* V4 #1834
• Update build to include patching tests
• Set internals visible for PatchingTests project.

This implementation will work with Postgres 9.6 and above.

[jeremydmiller]

It looks like a functional equivalent to the old Javascript version. Whenever we can beat Weasel into correctly determining the function body changes correctly, I'm ready to pull this in.

[mysticmind]

It looks like a functional equivalent to the old Javascript version. Whenever we can beat Weasel into correctly determining the function body changes correctly, I'm ready to pull this in.

I have retrofitted the functions as per the format where the delta is all fine with Weasel. That is why the unit tests are all green. So you are good to pull it in.