Actions API :: Cancel

Cancel method on the Actions API
Also a little bit of refactoring to move Actions related tests and code
into appropriate files.

http://reviews.vapour.ws/r/171/

Fix constants per review comments

use converter function
Merge pull request #910 from johnweldon/api-impl-cancel

Actions API :: Cancel

Cancel method on the Actions API
Also a little bit of refactoring to move Actions related tests and code into appropriate files.