Updates to StreamWatch Assessment Forms

[ptomasula]

Implement the following changes to the StreamWatch Schools assessment form.

• [x] Alphabetize user/investigator selection and provide search feature.
• [x] Remove the assessment type selection box.
• [x] Add 'not detected` option for the following parameters: Nitrate, Phosphate, DO, salinity, turbidity.
• [x] Remove Anaerobic as an option for the water odor field.
• [x] Remove sample size and reagent added fields from the turbidity section.
• [x] Provide text input for when other is selected to specify what other means.
• [x] Improve data validations (i.e. do not allow negative numbers to be input for concentration, properly bound pH, etc.).
• [x] Add new photo fields to form to allow upload and store of assessment/site condition photo.

[ptomasula]

Item 1 addressed in commits 4a8c9d3 and aa1b287.

[ptomasula]

Item 4 is controlled by a database field. I'll be addressing that item but adding a database migration script to our config repo which will remove this record from the database (and as an option from the form).