Improved OTU mapping (checkboxes on left, global fuzzy toggle)

@josephwb, @kcranston, @jar398: These changes reflect the most recent design consensus in #407 :
- OTU list has checkboxes on left to select OTUs for mapping
- Topmost checkbox (in header) de/selects all OTUs below
- Fuzzy matching (saved with the study) is toggled in the Mapping Options panel
- Simpler display of "adjusted" labels (don't repeat unchanged labels)