Suggestion: add warning of WMA Rating inaccuracy in scripting

[chrisjj]

Suggestion: on http://www.dbpoweramp.com/developer-scripting-dmc.htm for "Read ID Tag from File: .ReadIDTag", "Read ID Tag from File: .ReadIDTagElementValue" and "Write ID Tag to File: .WriteIDTag" that in the case of WMA Rating these do not actually read/write the tag (sic) value as claimed. They read/write "an approximation" which can be very far from the true value.