Better document current constraints on data increments and range

[scottdyer]

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 )

[scottdyer]

This is also sort of related to issue #87 In general, any of the tool's limitations as well as expectations for user imported data should be well specified.