(FACT-237) Add directed graph for handling dependencies
(FACT-237) Add aggregate resolution class
(FACT-237) Implement deep_merge for composing facts
(FACT-237) Implement deep_freeze for composed facts
(FACT-237) Use specific error classes for deep_merge and deep_freeze
(FACT-237) Freeze results of each aggregate chunk
(FACT-237) Define default aggregate action
Merge pull request #612 from adrienthebo/feature/facter-2/fact-237-aggregate-resolutions

Feature/facter 2/fact 237 aggregate resolutions