github:
closes: #4

* Handle and sanitize all input in extra block
* Use exported variables instead of daisy-chaining them through functions
* Improve error detection and handling
* Re-order functions in alphabetical order

New feature:
* `vcsh <repo> <gitcommand>` is synonymous with `vcsh run <repo> git <gitcommand>

* Be less aggressive when asking for confirmation
* Work independently from $PWD

github:
fixes #6

for github:
fix #9

Do not rely on XDG settings being the defaults

The examples may now fail/act weirdly if XDG variables are not set, yet it's an overall benefit to change this.

excludesfile = .gitignore.d/$REPO_NAME is set on

* init
* clone
* seed-gitignore

Renamed the original INSTALL.md to EXAMPLES.md and created a new
INSTALL.md