Fix date string parsing

SimpleDateFormat doesn't know how to parse dates containing the literal
'Z' as time zone, so we replace it with "+0000".
Merge branch 'bugfix/date-format' into boxer
Remove hardcoded colors for action bar spinner

Instead get a themed context from the action bar so the correct theme
is used for the spinner.
Merge branch 'bugfix/actionbar-dropdown-theme' into boxer