Merge branch 'feature/separated-ui'

Removes UI code from Admin API repository.

This will make developing the UI separate from the API easier, and also allow
using the UI separate from the API in the future. In the mean time, the module
has been modified to make the transition seamless for developers: the module
depends on the UI module, and the Module class ensures the UI module is loaded,
ensuring no changes are necessary in existing applications to continue working.
CS fixes (unused use statement)
Merge branch 'hotfix/cs' into develop