Add grid settings to preferences (#224)

- Allow origin to be either at the top-left corner or center of label (#174)
- For non-rectangular labels (cd, round, etc.) the origin will still
  always be at the center of the label.
- User controllable grid spacing

model/Distance.h

@@ -66,7 +66,6 @@ namespace glabels
 			QString toString( Units::Enum unitsEnum ) const;
 			QString toString( const QString& unitsId ) const;
 
-
 			Distance& operator+=( const Distance& d );
 			Distance& operator-=( const Distance& d );
 			Distance& operator*=( double f );