Adding Spring Framework resources, maven configuration, and view
Adding missed log4j.xml files and removing unneeded expression
evaluation library from POM
Adding controller, service, and model + their implementation
Change logs to info logs so that it is possible to track requests
Fix ArithmeticException when division returns a non-terminating decimal
Remove unneeded sysouts
Add error checking for multiple operators in a row and ending with an
operator.
Unit tests for CalculationServiceImpl and PostfixNotationExpression
Bug fixes associated with issues found through unit tests