[UPDATE] added java doc for classes
[UPDATE] added java doc for ExpressionTree class
update java doc
add test case for sin cos tan
[UPDATE] added java doc for classes
[Add] Test Case for Sine, Cosine, Tangent
[Add] test case of Csc, Sec, Cot
Merge commit 'f8245c5ad1a2d80f7be7a62701f5dbc63d5c04ab' into develop

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