foundational work for integrating the "credentials plugin"
step 1: figure out the UI and create new Class to handle auth

see this for details: https://issues.jenkins-ci.org/browse/JENKINS-20826
adding null-checks when retrieving username and/or API token
first pass at integrating with the "Credentials" plugin.
2nd pass at integrating with the "Credentials Plugin".
Functionality is working, but some clean-up may be needed
fixing compilation error when trying to convert between credential types
- major re-work of how authentication credentials are handled (it's all centralized to the Auth class now, now type of mediator-pattern between classes)
- full implementation of job-level authentication override
- cleaned up some of the jelly files
- bumping the "credentials" plugin to v1.9.4
- adding new dependency - "token-macro" plugin
adding a null-value check to Auth::getUsername()
implementing the ability to use tokens in all fields
Merge commit '8d621315059462a5578834aee4f5b3db601d8d79' into dev

# By elksson
# Via Maurice Williams (1) and elksson (1)
* commit '8d621315059462a5578834aee4f5b3db601d8d79':
  Token-Macro Support
  Added Token-Macro plugin dependancy
  Fixed Issue that caused Env Variable to be evaluated once
  Environment Variable Support

Conflicts:
	pom.xml
	src/main/java/org/jenkinsci/plugins/ParameterizedRemoteTrigger/RemoteBuildConfiguration.java
- adding additional clarifying comments
- cleaned up some code smell
prepping for new release:
	- updated pom.xml
	- updated screenshots and read me
	- new change log file
more README updates
Merge pull request #1 from morficus/dev

merging dev branch, ready for 2.0 release
[maven-release-plugin] prepare release Parameterized-Remote-Trigger-2.0