Stream compatatibility checks

[ccromjongh]

This PR adds support for compatibility checking of streams.

There are three types of checks:

1. Parameter checks (n, d, c)
2. Basic data & user type checks (number of bits equal?)
3. Advanced data & user type checks (do the classes match?)

One can select the strictness of the check through an implicit parameter of type CompatCheck. The strict check is default and checks if both streams use the same data-type. The weaker check (called Parameter) only checks the bit width of the used data-types.
One can select if errors should be thrown on incompatible streams or to print warnings (useful if checking all the issues in a design since execution stops at exceptions) by an implicit parameter of type CompatCheckResult.

The connection function := is now defined in the PhysicalStreamBase class and calls the correct data connection methods through matching and upcasting the arguments. This has the advantage that := can now use default arguments as there are no overloaded methods anymore.

:@= is the meta-connect function that only connects the meta signals of two streams and checks the parameter compatibility.
:~= is a shorthand for using := in an environment where implicit val errorReporting: CompatCheck.Value = CompatCheck.Params. I.e.: quick weak connect function.

Two examples/tests were updated because they had incompatible streams.