First functional version of the keyring manager window. Adds an FTP mount manager extension. Reserves file size only in cases when the option is checked and providers supports it. Adds an SFTP provider based on GIO. Fixes invalid exceptions in the keyring manager. Changes operations code to catch the correct exceptions. A lot of code refactoring and removal of unused imports. Properly saves the option used to reserve file size on copy/move. Unquotes URL encoded paths before changing path when navigating from bookmarks.