Add javadoc comments and Cleanup DynamicArray.java

[rbshealy]

Javadoc comments allow the user to understand the purpose of each method within the DynamicArray class.

cleanup within the class covers:
Condense imports
Initialize fields in constructor
Change binary shifting to simple multiplication reassignment for better understanding
Add brackets to multi-line if statements
Change name of size() method to getSize() to reflect purpose of the method
remove extra white-space
remove 2 lines of unnecessary commented out code

closes #1400

[rbshealy]

@StepfenShawn Could you kindly review this?

[StepfenShawn]

Thanks!