+ Added lock option that allows a plot owner to deny all actions of other players on their plots except players with a plot.world permission

* Changed plot sign:
- It needn't be placed on a plot anymore
- You can place it anywhere in the world with [Plot] in the first line and the plot name in the second line (It must be in the plot world otherwise it won't work!)
- The old sign type won't be supported anymore with this version!

+ Other players can't use beds on other plots that they not own

* Fixed some bugs