Better document current constraints on data increments and range

Provide better information about the format and increments of data. Current documentation is not as clear as it could be.

Example:
Data at 10nm gives the following error.
`Please double check the Camera Sensitivity data (e.g. the increment should be uniform from 380nm to 780nm).`
This error message does not make it clear that the data must be 5nm increments. In fact, it implies that data at any uniform increment between 380nm and 780nm should work.

(Source: http://acescentral.com/t/rawtoaces-calling-all-developer-types/1048/8 )

No documentation file or test is named; start by locating the documentation and the Camera Sensitivity validation message described in the issue. Update the relevant explanation or error wording so it clearly states the required 5nm increments from 380nm to 780nm, then verify that the documented constraint matches the current behavior.

Written by the indexing model from the issue text.