…culated attributes

Some are specific to the structure of CGAP portal schemas, but tried to
generalize as much as possible. Also includes partial draft of dependency
validation via topological sort.

… fxns

…ests for topological sort.

Resulted in edits within test files, including creation of a new
test file for topological sort, and changes in imports for
magma/metawfl_handler.py.

Changes included additions of different directed graph global vars
for testing -- tests for the topological sort on their way.
Also removed function for creating "forward dependencies" --
this version of topological sort works with "backward dependencies".

Addressed some prior comments. Future planned changes include
creating a class for the topological sort function to decrease
the number of command line arguments that are common among
several functions.

Also addressed some prior comments on draft.

Changes included merging some former magma utils fxns
into this class, and removing extraneous utils fxns.
Also includes new test file for this class.

Also wrote a draft of pytests

includes addition of custom Exception classes

…onstants. Got rid of duplication_flag.

…ocstrings