correct duration time in class detail page
add notice xml into detail activity
create front page xml for admin
split loginAndSignup page as two pages with front page
Merge branch 'f_admin_isolation' into develop
Merge branch '2.0' into develop
update gradle build
Update build script of gradle

Merge branch 'release-2.2' into develop
implement the function of exit survey
Merge branch 'f_exit_survey' into develop
update build script
Merge branch 'r_2.2.0' into develop