Refactor IDF parser code

[Anders-Markvardsen]

This issue was originally TRAC 6298

For example new component types beyond the original supported types (detector, source and samplePos) have been added, and likely more to come (for current list see http://www.mantidproject.org/IDF#Special_.3Ctype.3Es), which mean the method InstrumentDefinitionParser::appendLeaf() has been growing. Suggestion here is to do something similar to what was done for the geometric shapes

[Anders-Markvardsen]

@NickDraper (2013-04-29T09:49:55):
Moved to r2.6 at the end of r2.5

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@NickDraper (2013-07-26T13:55:00):
Moved to backlog at the code freeze for R2.6

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@NickDraper (2014-02-14T11:04:58):
Bulk move to assigned at the introduction of the triage step

[Anders-Markvardsen]

More than 3 years old