TofEvent and related: rename "TOF" to something more general like "X"

[mantid-builder]

This issue was originally TRAC 4736

Original Reporter: @jzikovsky

Since after ConvertUnits, the event's coordinate is NOT the time-of-flight. This can cause confusion for developers and possibly if the event gets exposed to python.

[mantid-builder]

@jzikovsky (2012-02-15T19:23:00):
Changed my mind about this; X is too generic.

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@AndreiSavici (2012-04-30T15:20:41):
This should really be done at some point

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@NickDraper (2012-08-10T12:45:12):
http://www.mantidproject.org/Release_Notes_2_2_Full_List

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@NickDraper (2012-10-28T11:42:52):
Moved to release 2.4

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@NickDraper (2013-01-28T09:23:33):
Moved at the code freeze for release 2.4

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@NickDraper (2013-04-29T09:50:06):
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

[NickDraper]

not important for now - archived