Introducing interface/ folder dedicated to the interface infrastructure and drivers...

Introducing interface/ folder dedicated to the interface infrastructure and drivers. Introducing interface_signal infrastructure to perform operations on interface port pins - this will create good abstraction layer for pin state operations at runtime and it is necessary to implement buffer configuration routines for SWD transport.

Change-Id: I03181343f97347e3595aeb9acf17efbd3e0d8671
Signed-off-by: Tomek CEDRO <cederom@tlen.pl>