Expose attrib setting API for testing, expose attribs in node UI [2/2]

Exposes ways to set node.discovery attributes in order to allow round trip testing
of the attribute system.

It made sense to have the attrib model be able to create a discovery mapping to make it
easy and consistent to set attributes on nodes.

The API allows directly injecting discovery json to the node model OR
  just setting the attribute using /nodes/[]/attribs/[] {value:setme}

The docs and tests have been updated with this functionality.

Additional bugs fixed in this pull
* application controller was not updating attributes correctly
* test jig was failing when delay was set as a string



 .../app/models/barclamp_test/attrib.rb             |   19 ++++++++++++++++---
 .../barclamp_test/app/models/barclamp_test/jig.rb  |    2 +-
 2 files changed, 17 insertions(+), 4 deletions(-)

Crowbar-Pull-ID: 1e1d51f3a00255be609e66e7e29427b97c63f986

Crowbar-Release: development