Minor cleanup of ArrayBasedStack.
Removed calls to toSTring from ReportingLinearStructure to let
Java do them implicitly.  (Why?  Because otherwise, things to
badly if a value is null.)
Add an array-based queue implementation, with bugs!
Started work on ArrayBasedStack.
Merge branch 'master' of https://github.com/Grinnell-CSC207/linear

Conflicts:
	src/taojava/util/ArrayBasedStack.java
Add files for priority queues.
Reversed meaning of "highest priority" in priority queues.
Add an adapter for Java's built-in priority queues.
Update intro comment in BuiltinPriorityQueue
Rename the primary priority queue experiments.
Merge branch 'master' of https://github.com/Grinnell-CSC207/linear
implemented unsorted priority queues