[Add] Try Sin function. [Not yet finish] to be continued.
[Add] Trigonometry Operators [Not yet finish]
[FIX] AffixConverter minor error
Refractoring and add Operator/OperatorFactory test cases
Merge remote-tracking branch 'origin/operatorSinCosTan' into develop

Conflicts:
	src/cal/AffixConverter.java
                src/cal/MathHelper.java
[ADD] Postfix operator handling
Rename AffixConverter test cases' name
[ADD] more complete JavaDoc for AffixConverter
Remove dynamic test case
Add Test Case for cot, cos, cdc [ToFix : NullPointerException]
isExpression() now can accept sin|cos|tan|csc|sec|cot
add factorial operator
 Pass Factorial and Cosine TestCase
Merge commit '0683838cec79ec2ebd228178d6691610d91b4852' into develop

Conflicts:
	src/cal/ExpressionTreeController.java
	src/testCal/ExpressionTreeTest.java

Refactor: extract BuidTree() from ExpressionTreeController to ExpressionTree
Merge branch 'master' into develop