updated many names from Number -> Measurand

[rowlesmr]

I was quite liberal with what I changed; if I though it could possibly have an SU, it got changed.

I didn't add *.2theta_range_inc|max|min, as errors in those values would be probably be cumulative over the entire range.

from #37

[vaitkus]

One little technical note. It is usually a good practice to change the last update date (_definition.update data item) of the modified save frames as well as modify the dictionary metadata accordingly:

• Change the _dictionary.date to the current date.
• Change the last value of the _dictionary_audit.date to the current date.
• Append a description of the changes to the last value of the _dictionary_audit.revision data item.

Definitely not a deal breaking thing, but helps to more easily keep track of all the changes in the long run.

[jamesrhester]

I agree with all of these. I'll add some su to the PR soon.