#113 - Use charset/collation currently in use by core tables

Addresses #113 (closed)

This moves the install sql code into the php file, which looks up what the core tables are using, and then sets the cdntax tables to use the same thing.

If testing on 5.28 or earlier it will still use utf8 regardless because I'm too lazy to copy/paste a function only available in core 5.29, and the default install for core for 5.28 is still utf8 anyway.

I've ignored upgrades pending dev/core#2237. So this is just for a fresh install of the extension.