Allow space characters in tag names

[tanius]

Currently, a space is treated as a tag separator, so it will cause the auto-suggest dialog to close (what follows after it will however not lead to creating a second tag on-the-fly).

Since for the initial version, we only want to allow one tag per annotation but with all characters that are allowed in Drupal taxonomy terms, this special behavior of space characters should be fixed. They should be included in tag names for both auto-completion and tag creation purposes.

(Not an urgent issue, just so we don't forget …)