Class search (in the GUI's class name filter) should be case-insensitive

[cyril-briquet]

(1) Searching for "MyClass", "myclass", "Myclass" should all return the same results.

If more than one class matches (e.g. if close syntactical variants do exist), all the matching classes should be returned.
(And this should be flagged as a bug as well.)

(2) Even better: make class search typo-insensitive, by e.g. implementing fuzzy search based on the edit distance (or Levenshtein distance).

(3) Dream: automatic completion of class names?

[andipabst]

I'd be willing to work on this. I will split it into two PRs: One for the case-insensitivity and fuzzy search, another one for the auto-completion.