Assessment values updates

[munnsmunns]

Updates to a #674 after review staff scientists:

• add POD type field, free text autocomplete
  • help text - "Point of departure type, for example, NOAEL, LOAEL, BMDL (10% extra risk)"
• add ADAF fields
• Rename 'system' to 'system or health effect basis'
• duration is related to the value, not the key study (change position in form and help text)
• change confidence to free text autocomplete
• confidence is related to the value, not the key study (change position and help text)
• change uncertainty factor to select box, with integer values
• restrict the drop-down for uncertainty factor to be 1, 3, 10, 30, 100, 300, 1_000, 3_000, or 10_000, 100_000, 300_000?
• change units to free text autocomplete instead of foreign key
• Add the scientific_pulldown.html to the template so users can add greek characters or superscripts
• change order of Value type choices to have IUR and OSF at the top
• change tumor/cancer type char limit to 128
• Update key study help text to say "Select existing study in HAWC for a key study. If it does not exist or there are multiple studies, leave blank and explain in comments"

Cancer form:

Noncancer form:

Summary table changes:

• Order summary table by value type
• Additional summary table fields