[functions] some more renaming
[functions.expression.base] remove unnecessary whitespace
[functions.constant] fix bug
[functions.interfaces] silence warnings
Merge branch 'master' of https://github.com/tobiasleibner/DUNE-Stuff
[la.container.pattern] add empty ctor
Merge remote-tracking branch 'tobias/master'
[functions] removed default implementation of order()

This commit might brake some user code, which is intended. There were far
too many problems related to the order defaulting to max(). So from now on
you always have to provide an order when deriving from
GlobalFunctionInterface!
[functions.expression] default to order 3