Inserting links to uploaded files does not escape spaces or special characters

[yoleg]

When clicking the "browse" icon in the "insert/ edit link" dialogue, users might upload and select a file that has spaces and/ or special characters. This URL should be escaped when being inserted.

Other notes:

• A system setting would allow this feature to be disabled if there are any objections to this (I cannot think of any).
• Perhaps this should be a JavaScript option when the file manager is called by any extension?