Remove MortarContextWrapper from the public API

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[INFO] Reactor Summary:
[INFO] 
[INFO] Mortar (Parent) ................................... SUCCESS [0.739s]
[INFO] Mortar ............................................ SUCCESS [10.978s]
[INFO] Mortar Sample ..................................... SUCCESS [26.382s]
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[INFO] BUILD SUCCESS
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[INFO] Total time: 40.389s
[INFO] Finished at: Thu Dec 12 13:14:37 PST 2013
[INFO] Final Memory: 30M/81M
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