In some situations (eg. refactoring) modules need to perform tasks that in fact have multiple phases, which all can
(should) run on the same data (sources, AST, parser, etc). Each phase is a separate UserTask, which may produce some
results (eg. change diffs) that are then processed outside of The Loop and eventually passed to the next phase, which
finishes the whole operation. From performance reasons it is advisable to reuse parser and its data in the subsequent
phases (tasks), which is currently not possible.

Since this is likely to have impact on the core interfaces in the API we should address this problem prior merging the
API to trunk.