Some minor wording changes

Most of these changes follow the convention (I can't find the documentation for this) of capitalizing only the first word of a menu item. All, IMHO, are easier on the end user, like nbz's suggestion of "Sent" becoming "Sent messages" or this one:

Send Message -> Send this user a private message

This makes it clear 1) that this is a private message and not an e-mail message and 2) that the message is specifically for the user whose profile page you're looking at.