Improve usability

[fetzerch]

• Make each step configurable by option (clone, fetch/reset, generate, compile, commit, push, push-description, (generate summary). Currently it's not possible to run push independently from fetch/reset
• Document the single steps better
• Document what templates generate what output
• Build errors (or better error in libretro-ctype) should prevent from pushing
• Log full path to summary.html and wiki.txt with a file:// link so that they can quickly be opened in a browser.

@garbear Maybe you can give some input on this. It's often easier to catch usability issues if you're not the author.

[garbear]

I solved the dependencies and tried building the cores already. All cores failed to build. I'll look into why tmrw