CLC-4154 - Add show more functionality to semesters & teaching cards

https://jira.ets.berkeley.edu/jira/browse/CLC-4154
CLC-4154 - Fix experience for teachers / GSI's
CLC-4154 - Fix error when no teaching / student semesters
Merge pull request #2868 from christianv/CLC-4154

CLC-4154 - Add show more functionality to semesters & teaching cards