Renamed getters.

Per http://golang.org/doc/effective_go.html#Getters:

    "Go doesn't provide automatic support for getters and setters.
    There's nothing wrong with providing getters and setters yourself,
    and it's often appropriate to do so, but it's neither idiomatic nor
    necessary to put Get into the getter's name. If you have a field
    called owner (lower case, unexported), the getter method should be
    called Owner (upper case, exported), not GetOwner. The use of
    upper-case names for export provides the hook to discriminate the
    field from the method."
First pass at wall fancification.

Doesn't work with RDivGenerator, and the top-left corner is still drawn
with '#'.

This should probably be moved out of the "connect" method, as not all
generators utilize Maze.connect.