Extract HKL info from SQW

[OwenArnold]

This issue was originally TRAC 4747

Apparently, SQW files contain hkl names as well as Q_eta, Q_zeta, etc.

Read these out of the SQW format if they exist and make them the dimension names, Q_eta etc should become the dimension ids.

[OwenArnold]

@NickDraper (2012-04-30T14:12:59):
Moved at end of release 2.1

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@NickDraper (2012-08-10T12:43:39):
Moved at the end of release 2.2

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@NickDraper (2012-10-28T11:38:51):
Moved to milestone 2.4

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@NickDraper (2013-01-28T09:23:02):
Moved at the code freeze for release 2.4

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@NickDraper (2013-04-29T09:49:39):
Moved to r2.6 at the end of r2.5

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@NickDraper (2013-07-26T13:54:59):
Moved to backlog at the code freeze for R2.6

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@NickDraper (2014-02-14T11:04:56):
Bulk move to assigned at the introduction of the triage step

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