usernameHider: Slightly adjust displayText description
usernameHider: Show true username on mouseover

Fixes #1139.
usernameHider: Update description
usernameHider: Add option to disable show on hover functionality
usernameHider: Disable showUsernameOnHover by default

Per discussion on #1698.
usernameHider: Only replace username portion

Per @andytuba's comments on #1698.
Merge pull request #1698 from mc10/username-hider

Show real username on mouseover with usernameHider enabled