Calculate name plate length based on username stripped of color codes

Note: This may well be fixed in 1.4, but it's impossible for me to check due to the lack of a Bukkit build.

Currently, adding colour codes to a user's name plate causes the length calculation for the blackbox under the text to be inaccurate, leaving a gap at the end as shown in the screenshot that is attached.

To fix this, the nameplate length needs to be calculated after using a version of the username stripped of all characters. This would allow colouring nameplates without this visual glitch, at least until the API is ready.