Update napi.h includes

[stuartcampbell]

This issue was originally TRAC 4179

At the moment the rpm and deb kits for nexus contain different include files and locations. Once both the kits are the same, then all the napi.h includes should be changed to nexus/napi.h

[stuartcampbell]

@stuartcampbell (2011-11-21T18:38:02):
Refs http://trac.mantidproject.org/mantid/ticket/4047. Move NeXus header reference back to napi from nexus/napi.

This will be put back again once all the nexus kits are in sync.
I have created a ticket for this - refs http://trac.mantidproject.org/mantid/ticket/4179
23c2b69

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@NickDraper (2012-01-09T09:45:01):
Moved to iteration 33 at iteration 32 code freeze

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@NickDraper (2012-04-30T14:15:33):
Moved at end of release 2.1

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@stuartcampbell (2012-08-06T13:59:28):
This is waiting on NeXus 4.3 being released (and kits available) on all platforms.

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@NickDraper (2012-10-28T11:42:50):
Moved to release 2.4

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@NickDraper (2013-01-28T09:23:31):
Moved at the code freeze for release 2.4

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@stuartcampbell (2013-02-15T20:32:27):
Remove top level NeXus headers.

These should be inside the 'nexus' subdirectory.
refs http://trac.mantidproject.org/mantid/ticket/4179
42a5a2f

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@stuartcampbell (2013-02-15T20:58:51):
Trying quick fix for CMake FindNexus problem.

refs http://trac.mantidproject.org/mantid/ticket/4179
1be8ee4

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@stuartcampbell (2013-02-15T21:06:43):
Updated nexus include paths. refs http://trac.mantidproject.org/mantid/ticket/4179
3d5336d

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@stuartcampbell (2013-02-15T21:28:20):
Update FindNexus cmake file. refs http://trac.mantidproject.org/mantid/ticket/4179
e662d90

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@stuartcampbell (2013-02-15T21:35:34):
Reverting removal of headers

Will look again on monday morning.
refs http://trac.mantidproject.org/mantid/ticket/4179
1c54ec4

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@stuartcampbell (2013-02-15T21:37:05):
Revert changes for now. refs http://trac.mantidproject.org/mantid/ticket/4179
cf815b9

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@NickDraper (2013-04-29T09:50:05):
Moved to r2.6 at the end of r2.5

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@NickDraper (2013-07-26T13:59:10):
Moved to the Backlog after the code freeze for R2.6

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@NickDraper (2014-02-14T11:07:57):
bulk move to assigned at the into of the triage step

[stuartcampbell]

I have updated our cmake and so this should no longer be necessary.