Gaudi::Functional: Add possibility to query input/output location by type

In addition to:

  inputLocation<N>()

where N is an integer, to get the key of the N-th input location, one can now also do:

  inputLocation<T>()

where T is the type. Note that if there are multiple T used as (input)argument, this will not compile.

Note: includes !1007 (merged)