Fixed exceptions being thrown when a piston is moved in a non-plot world
Fixed builder list issues with the new UUID system

* The builder list was not imported correctly, and broke the plot file
* The builder list was not serialized properly on file
* /iplot info was displaying technical information (class name and UUID) instead of player names
Potential NPE fix in the case a player somehow does not exist
Code style convention fix
Merge pull request #56 from phipla/master

Fixes for the 1.7.9 version of InfinitePlots