Improve Monte Carlo simulation in LeBailFit and enable to refine background

[wdzhou]

Improve the Monte Carlo simulation algorithm in LeBailFit. Here is a list of work in mind.

1. As a new value of a parameter proposed, it will be checked against the specified boundary of this parameter. There can be 3 ways to treat the situation that the new value is out of boundary, (a) half distance to the boundary, (b) reflect from boundary, and (c) periodic boundary. A random number can be used to determine which method to use;
2. Enhance the book keeping of parameter values in Monte Carlo algorithm.
3. The background is refined outside of LeBailFit presently. Enable LeBailFit to refine background polynomail parameters. It might improve the refinement.

[wdzhou]

This issue was originally trac ticket 6747

[wdzhou]

http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/LB4853b2.hkl
(uploaded by @wdzhou on 2013-04-18T18:18:36)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/nom60b4.irf
(uploaded by @wdzhou on 2013-04-18T18:18:46)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/NOM_11848-4.dat
(uploaded by @wdzhou on 2013-04-18T18:18:56)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/nom_bank4.irf
(uploaded by @wdzhou on 2013-04-18T18:19:08)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/refine_background.py
(uploaded by @wdzhou on 2013-04-18T18:19:26)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/refine_profile.py
(uploaded by @wdzhou on 2013-04-18T18:19:35)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/set_param_limit.py
(uploaded by @wdzhou on 2013-04-18T18:19:44)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/setup_preview-1.py
(uploaded by @wdzhou on 2013-04-18T18:20:11)

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http://trac.mantidproject.org/mantid/raw-attachment/ticket/6747/setup_preview-2.py
(uploaded by @wdzhou on 2013-04-18T18:20:20)

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