Merge pull request #1251 from mitraj/dev-branch

Added New images for no-assignment classpage.
UI Change for sub dropmenu on header bar implemented
Rendering the Standard, District Libraries from properties file.
Merge remote-tracking branch 'upstream/dev-branch' into dev-branch

* upstream/dev-branch:
  Added New images for no-assignment classpage.
  DO-5203 issue has been fixed.
  Handled null at class pages.
  "Modified and added new static text in MessageProperties file"

Conflicts:
	src/main/java/org/ednovo/gooru/shared/i18n/MessageProperties.java
	src/main/java/org/ednovo/gooru/shared/i18n/MessageProperties.properties
Merge pull request #1252 from anilgooru/dev-branch

Rendering the Standard, District Libraries from properties file.
added standard code for filter
Merge pull request #1254 from nutan-gooru/dev-branch

added standard code for filter
Fixed California State Standards stays checked even if no CA standards are selected
Merge branch 'dev-branch' of https://github.com/Gooru/Gooru-Web into dev-branch
Merge pull request #1255 from nutan-gooru/dev-branch

Fixed California State Standards stays checked even if no CA standard… …
Ui changes in home view.
Fixed issue with contributors link.
Merge remote-tracking branch 'upstream/dev-branch' into dev-branch

* upstream/dev-branch:
  Fixed California State Standards stays checked even if no CA standards are selected
  added standard code for filter
Merge pull request #1257 from anilgooru/dev-branch

Fixed issue with contributors link.
Library:collection and quiz highlight issue rectified.
Merge branch 'dev-branch' of https://github.com/Gooru/Gooru-Web into dev-branch
Merge pull request #1258 from VinRudramurthy/dev-branch

Library:collection and quiz highlight issue rectified.
Fixed issue on not clickable on join button
Merge remote-tracking branch 'upstream/dev-branch' into dev-branch

* upstream/dev-branch:
  Library:collection and quiz highlight issue rectified.
DO-5245 issue has been fixed.