Disable aimField box in intitial user information pane

This box to enter the aim for the user is not currently active or used. Since it is not used, it shouldn't be active until we build in the functionality for IM messages to be sent. My user model can handle the IM field being empty/null.
Merge pull request #291 from sfmailand/sbl-dev

Disable aimField box in intitial user information pane
Tested by: ajthompson