Make level code related error messages more user-friendly
Make error message removable by user click
JSHint compliance
added level and author name to Level class (and serialization)

(No forward compatibility I'm afraid!)
Add level+author name display
Refactor: add setLevel() function
Allow user to change level title
jshint compliance
Line painter: first commit

This branch tries to implement the paint-line mechanic of the original game.

This commit contains the (slightly modified) code made by BlasphemousMoons, which pretty much works but should be cleaned up.
Moved line painter code into its own script/class
changed line color and size