make month table min-height: 90px to remove jumpy switching
add booking block destroyed check
fix several small corner cases in timecard month graph
change everything to use dateranges

Conflicts:
	phprojekt/application/Timecard/Controllers/IndexController.php
	phprojekt/htdocs/phpr/Statistics/WorktimeMonthGraph.js
	phprojekt/htdocs/phpr/Statistics/WorktimeMonthTable.js
	phprojekt/htdocs/phpr/models/Timecard.js
enhance datetextbox to support special values

we now support the values 'lastOfMonth' and 'firstOfMonth'
use datetextbox special values in statistics view

Conflicts:
	phprojekt/htdocs/phpr/template/statisticsView.html
add a function to schedule the month widget update

that way we can collect all the 'update' callbacks on startup
and still just send out one request
update month widgets on time range change
add attach point for start end date
fix unexpected behavior when selecting end date

the user does not expect the end date to be exclusive
Merge pull request #369 from exi/PTC-159-choose-date-range

Ptc 159 choose date range