WebPositive: Now that it lives in the tree, get rid of the copied shared code.
WebPositive: Fixed untranslated empty tab region tool-tip.
WebPositive: Removed wrong license text from all files ...

 ... which were technically never distributed by Apple nor
 are derived from code distributed by Apple. Only BrowserApp
 and BrowserWindow were originally derived from code that used
 to be part of WebKit and was distributed by Apple.