Several bug fixes and Python SFF/SF reference implementation

Introduced a CheckedFuture callback implementation
Started using CheckedFuture for some transactions
Fixed a bug with SB REST where the URI was not extracted from model correctly
Fixed handling of exceptions in SB REST code
Added LOGs to several transaction
Added a new directory and Python reference implementations of SFF/SF
Fixed minor bugs with SFC python regression

Change-Id: I56811650900eb44818ae144368969bb01a8d5274
Signed-off-by: Reinaldo Penno <rapenno@gmail.com>
Merge "Several bug fixes and Python SFF/SF reference implementation"