added system.md
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Merge branch 'master' into 784865
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updates to system.md
finish draftin system.md; update cfx-tool
fixing up system.md
Merge remote-tracking branch 'origin/784865' into 784865
Merge branch 'master' into 784865
Bug 784865 - Document the system module; r=@ZER0
Merge pull request #707 from wbamberg/784865

Address review comments, and fix bug 784865: document the `system` module