Change view for loose content / Refactor data ingestion & loose content management

Change view for loose content:

• Add a button for on the fly content group creation
• Have check boxes to select content that goes into a new group
• Remove toggle buttons for locking questions and enabling answers

Refactor storage data:

• Implement a global storage to handle session and local storage
• Move content groups, room and device info into in-memory data store
• Use constants for storage keys

Add resolvers:

• Implement room resolver to ingest the current room into components
• Implement content group resolver to ingest current group data into components

Refactor loose content:

• Rename 'Content without a group' into 'Loose Content'
• Implement on-the-fly content group creation from loose content
• Split components for handling content groups and loose content
  • Both inherit from a common component

Refactor content group management:

• Delete and post a content group when renaming it
  • Backend disallowes renaming content groups because of collision problems with names

!Closes #498 (closed)