new doc for string lib
new doc for string lib

ldtri0209/robotframework,fiuba08/robotframework,fiuba08/robotframework,ldtri0209/robotframework,waldenner/robotframework,ldtri0209/robotframework,waldenner/robotframework,fiuba08/robotframework,waldenner/robotframework,waldenner/robotframework,fiuba08/robotframework,waldenner/robotframework,ldtri0209/robotframework,fiuba08/robotframework,ldtri0209/robotframework