Plugin property mapping w fixed tests

[Jesus-Osuna-M]

Original PR: #31

Enhancements:

• PropertyResolver added so that properties set on the project/framework level are retrieved
• A new property can be set on project/framework level to force plugin to use proxy-settings set on the JVM
• Failing unit tests were fixed
• Small refactor to make code more legible

The new property needs to be set on project (or framework):

project.plugin.WorkflowStep.edu.ohio.ais.rundeck.HttpWorkflowStepPlugin.useSystemProxySettings=true
project.plugin.WorkflowNodeStep.edu.ohio.ais.rundeck.HttpWorkflowNodeStepPlugin.useSystemProxySettings=true

This tells the plugin to use the JVM proxy settings as set here

[ronaveva]

please add unit tests for the new methods

[ronaveva]

LGTM, lets make sure this gets into the bug bash