properties to handle q, g, V_bar, V_tild + minor clean up

* can now treat self.q, self.g, self.V_bar and self.V_tild as
  attributes, as they are now governed by properties

* indicate that some functions are "protected"

* rename test file to test_known_results.py to facilitate unittest:
	python -m unittest discover

* add argument to all construct functions for (planned) potential
  exclusion of absolute flows from constructs (e.g. to save memory)

 On branch speed_encapsulation
 Changes to be committed:
	modified:   pysut.py
	modified:   tests/__init__.py
	modified:   tests/test_allocations_constructs.py
	renamed:    tests/known_results.py -> tests/test_known_results.py
All constructs speed with spares matrix + return flows now optional

* hidden properties return sparse versions of key variables
	self.__sU returns the sparse matrix of self.U

* All construct equations are now performed with sparse matrix, which
  greatly speeds things up, considering how sparse V, E_bar, Gamma, PHI
  and Xi are...

* With parameter, all constructs can now avoid returning the
* unnormalized flows.

* additional unit tests

 On branch speed_encapsulation
 Changes to be committed:
	modified:   pysut.py
	modified:   tests/test_allocations_constructs.py