Consolidated URLs with constants.

Throughout the code, tests included, we have many variables pointing to
a URL which is in turn used for some of our tests or default values. I
have created several new constants for these URLs and updated the code
accordingly.
Merge pull request #1454 from omaciel/update-urls

Consolidated URLs with constants.
Documentation update for sam fencing with code samples
Merge pull request #1453 from sthirugn/sam-fencing-doc

Documentation update for sam fencing with code samples