Update to 1.7.9 tag from main upstream repo (gothfox/Tiny-Tiny-RSS repo)

This is huge, which is bad, I know. It works though.

This is what I've done:
- Remove everything from php/ except config.php
- Download the tar.gz for the latest tag from https://github.com/gothfox/Tiny-Tiny-RSS
- paste everything from there into php/
- Rebase config.php to get latest necessary options

I've tested it and it works great.

While I'm here, it kinda sucks that upstream commits aren't mapped to this repository in some way. I'm guessing a submodule isn't an option because we need a config .php file. I don't know of any better ways, apart from possibly having a separate remote for upstream, and then manually merging everything from there to php on the master branch. There should definitely be some sort of traceability though, otherwise git is wasted on this I feel.