Removed all type prefixes - a byte indicating what kind of id it is (V/E/P). This means that element ids for vertices and edges need to be unique (can't have element id "A" for both a vertex and an edge). But this is a reasonable price for simplification.
Use AccumuloElementId for node/edge ids now, rather than arbitrary objects. Ids passed in to addVertex, etc. will be converted to String and used. getId() returns AccumuloElementId which may differ from what was passed in when creating vertices/edges.
Added getVertices() for a range of ids
Added ElementType to distinguish vertex and edge
Created AccumuloIdManager which will manage id-related translation from AccumuloElementId to Text storage in Accumulo
Rename constants to make them more consistent with usage
Removed getIdRow from AccumuloElement to ensure consistent usage of AccumuloIdManager
* Removed global vertex/edge lists. Originally these were used to be able to iterate over all vertices/edges. Not needed now because element ids are prefixed.

* Add row deletion iterators to the graph table which makes deleting elements faster and easier.
* Updated documentation
* Retooled get{Vertex,Edge} to use get{Vertices,Edges}InRange

* Fixed bugs in get{Vertices,Edges}
Documentation and notes