SlyEdit: For sysops, when importing a file, SlyEdit can optionally send immediately (if not, edit the message before sending). Useful for posting ANSI files

SlyEdit: For sysops, when importing a file, SlyEdit can optionally send immediately (if not, edit the message before sending). Useful for posting ANSI files. Also, made a small refactor: Used user.is_sysop rather than SlyEdit's own variable to store whether the user is a sysop. Updated the minimum Synchronet version to 3.15 for user.is_sysop