Add helper functions to array tree and array tree node

For the array tree node some of the functions (i.e higlight, index, css,
swap) belonging to the array have been exposed to the node. Additionally
the move value function has been added to the array tree prototype to
facilitate movement between nodes.
Update array tree example for testing
Finish remaking first three diagram and slide shows
Merge branch 'master' of https://github.com/OpenDSA/OpenDSA