UI tweaks and image fixes

Fixed issue where indented numericInputs' labels would line break before
the right edge of the input.

Fixed issue with disappearing images (local bug: set OneDrive to keep
images folder offline)
Error Handling and Bug Fixes

NEW: Intercept errors in uniroot() and pwr.norm.test() and print
user-friendly message on error
NEW: Error handling for blank inputs
IMPROVEMENT: Better condition to identify DTR selection
IMPROVEMENT: Fixes in one-sided testing--default to "greater" for
pwr.norm.test() and take absolute value of effect size input