Colonising Added

Colony Wagons can now be built but Trade Caravans still need to be added
in
Added Cost and Dimension properties to all Buildings

Not yet compiling.

Defined Shared ReadOnly s_cost & s_dimensions in each Building subclass.
Added MustOverride Cost and Dimensions methods to Building base class
which are then Overridden in each subclass to returned their Shared
value.

Began making changes to the leftPanelButton implementation to use Costs
and Dimensions as exposed by Buildings.

Need to make further changes as change Costs from an array of Integer
where each index is a different resource, to a Dictionary indexed by
Resource with Integer values for the cost.  This is more space efficient
and saves having to revisit all building subclasses when new kind of
Resource is added.  Need to make further changes here to use an
Enumerator over the Dictionary to access the elements within it.