Fix error when installing extensions from Network Admin
Replaced all occurrences of Stream Premium with Stream Extensions, fixes #494.
Merge pull request #495 from x-team/issue-494

Replaced all occurrences of Stream Premium with Stream Extensions, fixes #494.
Merge pull request #492 from x-team/issue-491

Fix error when installing extensions from Network Admin
Fix for #464, 'inactive' now sits where it should
Merge pull request #503 from x-team/issue-464

Fixing styling issue for 'inactive' text on Extensions screen.