DisposableCollection
   AbstractReferenceCollection
   ReferenceCollection
   SyncReferenceCollection

Lack of documentation, especially for non-trivial but pervasively used
types is, IMO, a hindrance to the widespread adoption of the platform.
Imagine STL or any other major library expecting developers to learn
and understand its various facilities by reading the code line-by-line.
It significantly increases the learning curve and makes the platform
less approachable.

Where I am having to do such line-by-line studying of the code to
understand these essential utilties, I'll be making contributions to
hopefully bring some relief. However, I do think this technical debt
should be tackled in a more comprehensive and intentional manner now
that Theia has presumably reached some sort of critical mass.

Improved description based on Martin's feedback.