filter by start/due-date

add option to ~~TODOLIST~~
  startbefore:<date>
  startafter:<date>
  duebefore:<date>
  dueafter:<date>

<date> can be:
Y-m-d like 2014-06-12
or a value like +10 or -10 or 0
invalid values will be substituted with todays date
style for tododates

new style for tododates
smallet text for users and dates
add options

* usernames for <todo>
* start/due-date filter for ~~todolist~~
set date 2014-06-14