Added Ui test cases for FeedbackPage

-> added more sessions in test data and changed html comparing files
accordingly
-> added html compare test for typical success case
-> added link tests that check all links
Added link test cases including target checks

Added functions that help to click the relevant link and return the New
Page as the return object.

The other page files now have a "isCorrectPage" function used to confirm
that the link worked.
completed action tests for FeedbackPageUiTest

-> revamped all the test cases be more effective and efficient
-> removed one test case
-> added helper functions in the InstructorFeedbacksPage.java
made the datepicker functions stateless
Merge branch 'master' of https://github.com/TEAMMATES/repo into Issue1900
standardised attribute names and refactored

-> created a method for recurring statements
more refatoring to create fillTime functions

allow pageUiTests to be able to edit the time values separately
slight change in behaviour of datePicker
started with DatePicker Test
completed ui test for datepicker

-> added helper functions in InstructorFeedbacksPage
-> added test cases in InstructorFeedbacksPageUiTest

NOTE: tests are volatile since they depend on focus/out-of-focus events.
Thus any change in the focus state of the browser will cause the test to
fail
Merge branch 'master' of https://github.com/TEAMMATES/repo into Issue1900
test cases to ensure datetime elements enable/disable properly
Merge branch 'master' of https://github.com/TEAMMATES/repo into Issue1900
added comments regarding the test cases
Merge branch 'master' into Issue1900
[1900] Clean up InstructorFeedbackPageUiTest

fixes #1900