Fix datepicker in default theme.

- Don't use mm/dd/yyyy format as this will be parsed inconsistently by PHP's
strtotime() depending on locale settings. Use ISO date format instead.

- Make sure the "This Week" quicklink works even if the week crosses into
  the following month.
Merge pull request #1126 from solarissmoke/datepicker-fixes

Datepicker issues in default theme.
Fix fatal error in stats model

Fixes fatal error in stats model if there are connection problems
with the tracker server
Merge branch 'solarissmoke-bug-stats-issues' into develop
Closes #1140. Proper replacement of carriage return character to sort out CSV import issues
Closes #1113 . Removing whitespace from default values of custom form fields before attempting to match them with form field responses (which are already trimmed out before report submission) :D