RootNode and InternalNode Probe Methods

[danrbailey]

This PR adds a bunch of new "probe" methods to fill in some gaps in the API in being able to query child nodes as well as adds some additional convenience methods.

RootNode

The root node adds convenience methods to query the child nodes (as opposed to needing to supply a template parameter probeNode<ChildT>(const Coord&)). In addition, there are new probe() methods that query whether a key exists (and returns false if not) and returns either a child node or a value and active state otherwise. Finally, a templated probeNode() method that can be called on a const RootNode has been added.

Here are all the new RootNode methods:

ChildNodeType*       RootNode::probeChild(const Coord&);
const ChildNodeType* RootNode::probeConstChild(const Coord&) const;
const ChildNodeType* RootNode::probeChild(const Coord&) const;
bool                 RootNode::probe(const Coord&, ChildNodeType*&, ValueType&, bool&);
bool                 RootNode::probeConst(const Coord&, const ChildNodeType*&, ValueType&, bool&) const;
bool                 RootNode::probe(const Coord&, const ChildNodeType*&, ValueType&, bool&) const;
template <typename NodeT> 
const NodeT*         RootNode::probeNode(const Coord&) const;

InternalNode

The internal node adds convenience methods to query the child nodes (as opposed to needing to supply a template parameter probeNode<ChildT>(const Coord&)). In addition, there are also methods that allow querying from an offset (and ensures the offset is not out-of-bounds) as well as being able to pass in value and active state reference variables that are populated if a child node is not present. Finally, a templated probeNode() method that can be called on a const InternalNode has been added.

Here are all the new InternalNode methods:

ChildNodeType*       InternalNode::probeChild(const Coord&);
const ChildNodeType* InternalNode::probeConstChild(const Coord&) const;
const ChildNodeType* InternalNode::probeChild(const Coord&) const;
ChildNodeType*       InternalNode::probeChild(const Coord&, ValueType&, bool&);
const ChildNodeType* InternalNode::probeConstChild(const Coord&, ValueType&, bool&) const;
const ChildNodeType* InternalNode::probeChild(const Coord&, ValueType&, bool&) const;
ChildNodeType*       InternalNode::probeChild(Index);
const ChildNodeType* InternalNode::probeConstChild(Index) const;
const ChildNodeType* InternalNode::probeChild(Index) const;
ChildNodeType*       InternalNode::probeChild(Index, ValueType&, bool&);
const ChildNodeType* InternalNode::probeConstChild(Index, ValueType&, bool&) const;
const ChildNodeType* InternalNode::probeChild(Index, ValueType&, bool&) const;
template<typename NodeType>
const NodeType*      InternalNode::probeNode(const Coord&) const;

[kmuseth]

see omments

[danrbailey]

Addressed all the feedback in this PR, thanks!