1. add course access test for newly joined instructor in adminHomePageUiTest
2.found and fixed a typo in studentHomePage
3. fixed related tests

Dev Green
add condition for staging server test
fix testing purpose typo
1.add a method to recover a html-sanitized string to original encoding
2.add a test for above method
3.call this method in instructorCourseStudentListDowloadAction to ensure the display is in correct format
change indentation
add test for student list downloading action with special team name
Disabled the printing of "ignoring tooltip..."
[2274]'/' in team name is messed up in the csv download

fixes #2274
Merge branch 'master' of https://github.com/TEAMMATES/repo
[2266]add tests for sample course of newly joined instructors

fixes #2266
adding one question
add another question in help page
instructorHelpPage
add comments for access control
add comments
add comments
Updated features.html to reflect V5.x features
Removed feature screenshots no longer used
Updated the text in index.html to reflect V5.x
Updated images in the homepage