Check that user submitted values are sane

[DougEdey]

Converted from SourceForge issue 1501033, submitted by andrew_avis

Some values should be checked for sanity. EG: you can enter 36 instead of 1.036 for a fermentable ppppg. In this case, the UI should convert 36 to 1.036 before setting the ppppg, or report an error. Acceptable range should be 1.000 to 1.050.