Logistic Regression: Refactor iteration controller

Replace the iteration controller with the one defined in utilities.

Other minor changes:
* Move all code into Python
* All internal functions now starts with __
* Added argument validation for logistic regression
* In cv_utils, added functions to help return array from Python to older
  versions of database system. However, its usage in logistic regression
  turns to be unnecessary
* Updated control.py_in to evaluate all forms of expression
* Removed old code, added comments
Logistic Regression - Refactor iteration controller: Pass install-check

* Made the array[...] expression acceptable
* Allow tolerance to be zero
* Disable the check on dependent variable, because a boolean expression
  like 'crimeRat >= 110' can be passed into the function at the position
  of dependent variable