Add PII_FOREACH_TEMPARG

This macro is useful for repeating a function for all arguments in
a template argument pack.
Fix ToValue trait

The former definition removed const.
Enhance unit test for type traits
Fix signal/slot connection

The signature of a signal in PiiProbeInput changed some time ago.
Adapted the code to the new signature.
Add C++11 function call helpers

- Implemented callWithTuple() and callWithTuples() that let one to call
  functions with unpacked tuples.

- Added MemberFunction structure that wraps a member function call.
Add a generic function-wrapping operation
Add unit test for PiiFunctionOperation
Add missing #include
Remove empty space at line ends
Add functionoperation to SUBDIRS
Fix handling of const member functions
Fix function pointer type handling

Function pointer type (e.g. "void (*)()") was confused with function type
(e.g. "void()") which caused unnecessary complexity.