Tree-like data structures and reorganization of dynamic import modules

[timbernat]

Many types of Python data structures lend themselves very naturally to being recast as trees; look no further than Python packages or pathlib Paths (where modules and file paths are the corresponding "leaf" objects, respectively). A unifying treatment of the correspondence to trees for abstract types would go a long way in eliminating boilerplate and increasing cohesiveness for may applications.

Further, the addition of a tree-like interface to Python packages (based on anytree) would make much of the current genutils.importutils obsolete, both in terms of dynamic imports and GNU tree emulation.

These two observations motivate several restructures to polymerist which would greatly simplify and systematize how tree and package
operations are handled

• Implement a TypeToNodeCorrespondence abstract base class which allows one to define treelike behavior for arbitrary classes
  • Provide a concrete implementation for Path objects
  • Provide a concrete implementation for Python packages
  • Provide generic API for traversing and filtering through trees by arbitrary conditions
  • Provide conversion methods to networkx Graphs
• Convert the current importutils module into a subpackage
  • Deprecate reimplementation of GNU tree printing in terms of anytree's analogous representations
  • Absorb pyimports into this new subpackage
  • Remove full polymerist package tree into from toplevel init.py
• Reimplement genutils.fileutils.filetree with actual filetrees
• Write unit tests for all of the above

[timbernat]

Resolved by PR #29