Check extension path

It will replace enabled extension with installed one via "make install".
This is primarly to ease up development with jhbuild.
Simplify window geometry hints
Strike-through tasks that are done
Unify license text
Handle task activation signal
Hide the filter button

There seems to be a GTK+ bug concerning used symbolic icon
Show default license notice
Move tasklist view to TaskListPane class
Check extension path

It will replace enabled extension with installed one via "make install".
This is primarly to ease up development with jhbuild.
Simplify window geometry hints
Strike-through tasks that are done
Unify license text
Merge branch 'tasklist'

Conflicts:
	lib/about-dialog.vala
	lib/main-window.vala