#11 Associate NDB Measurements to Units on the fly

Right now the Units page has a list of aliases which map NDB units to internal units. If no mapping exists, the app fails to calculate a density when adding the food. Additionally, there is a loss of information because different versions of the units (such as chooped, ground, large-whole, etc.) are lost. This information is useful as some recipes might call for a whole onion versus 1 cup of chopped onions. Instead of relying on an alias to map from NDB to internal Units, use the alias as a suggestion and prompt the user to choose a mapping.