Fix: Allow special charaters in node titles

[falk-werner]

Instead of restricting the user to allowed file names, we should also allow special characters in note titles.
I think, the most restrictions come from windows file systems (see below).

I had two possible solutions in mind:

• use URL encoding for node titles
• save note titles somewhere else

The quickest solution and the one which is picked here is to use URL encoding. However, we do not encode every character but only special characters which are prohibited in file names (<, >, :, ", /, , |, ?, *) and the escape character (%). For decoding, a full URL decode is used. This is safe as long as all notes are created by note.py or any other tool which encodes file names the same way.

Another solution will be to store the full title somewhere else in the note's directory. Maybe some metadata.yml. We should try to keep the directory name an title in sync, but we are not forced to. This solution will take more effort but the metadata.yml might come in handy later, when other meta data should be stored (e.g. tags).

@hmlampe: Please let me know, which solution you prefer.

References:

• Windows file Naming rules

[hmlampe]

I added a test for this feature, is this okay with you?