VolumePanel: Optimizations

-Place MSG_TIMEOUT as a constant so compiler will optimize the rest for
us.
-Reload pref instead of making new instance.
-Place Setting Transparency in try..catch because if mDialog is not
found, skip the whole thing and continue with  setting timeout
-Remove unnecessary getAlpha check for <25 and >100 because we already
have a slider which limits it.
Version Bump (v1.8)