Move general-purpose classes into util and problem sub-packages
Merge in base interface types
Merge pull request #3 from dmlloyd/subpackages

Move general-purpose classes into util and problem sub-packages
Merge pull request #4 from dmlloyd/context

Collapse context interfaces
[MSC2-30] fixing Registration's addDemand() and removeDemand() methods
[MSC2-33] MSC2 API calls must be async