In this implementation of MyUnit, is where all the public functions
that didn't already get implemented are implemented. The functions
that are identical are implemented a level up in the directory
heirarchy. All the implementations sitting at this level are specific
to Impl2. The same files exist for the public functions in
Impl1, but they have implementation specific to Impl1. The
non-public functions may be different between 
the two (in this case there is mu_localFoo specific to Impl1, while Impl2
has two local functions, mu_localFoo1 and mu_localFoo2). 
Please note that following the naming convention, the functions have
prefixes identifying where they came from, but are not the same as the
public function prefix "MyUnit". In this example we use "mu_" for "MyUnit".
The local prefixes are encouraged but not enforced.