CODE REFACTOR: refinement criterion is encapsulated in a function which is given as an input argument tree construction function
Minor changes
BUG FIX: fixed the bug for constructing the tree with values of a function at a given time
Updating the test units of tree_data according to the latest changes
Modified the advection on the tree so that tree of next time step can have any arbitray depth and does not need be the same as current time step:
Implemented the adaptive refinement of the tree
moving test files to a separate directory
Implemented adaptive coarsening of the tree
Minor changes
Merged the adaptive coarsening and refining algorithms into one algorithm which is more efficent
code restructuring