[JENKINS-16364] Add support for Build Dsl job type.

This will allow creating build flow jobs by passing in the dsl block.

This change does not provide support for making the dsl block pretty; it
must be escaped for the resulting job to be pretty printed.

Usage:

  buildDslBlock( <build dsl text, escaped or flat> )

Example (simple):

  buildDslBlock('build ("job1")')

Example (escaped):

  buildDslBlock("parallel( \n { \n \" job1 \" } \n) " )

Example (passing in a variable's value, so the created job has
the value in the text of the dsl block):

  buildDslBlock('build("${BUILD_TAG}")')
  End result in build DSL node: build("my-base-job-dsl-job-12")

Example (passing in a variable, so the end-result is a created job
that has the variable (and not its value)):

  buildDslBlock('build("\${BUILD_TAG}")')
  End result in build DSL node: build("${BUILD_TAG}")
[JENKINS-16364] Update support for Build Dsl job type; refactor naming conventions.

Note that the dsl block must be triple quoted if it's pretty printed.

Updated usage below.

Usage:

  buildDslBlock( <build dsl text, escaped or flat> )

Example (simple):

  buildDslBlock('build ("job1")')

Example (pretty):

  buildDslBlock("""
    parallel(
        { " job1 " }
    )
    """)

Example (passing in a variable's value, so the created job has
the value in the text of the dsl block):

  buildDslBlock('build("${BUILD_TAG}")')
  End result in build DSL node: build("my-base-job-dsl-job-12")

Example (passing in a variable, so the end-result is a created job
that has the variable (and not its value)):

  buildDslBlock('build("\${BUILD_TAG}")')
  End result in build DSL node: build("${BUILD_TAG}")
Added support for the Github pull request builder plugin
Move appendOrReplaceNode to the AbstractHelper to keep it DRY; Rename buildFlowBlock to buildFlow.
addressed comments : spec cleanup & mandatory closure
Added missing options for the BuildPipelineView
Enum for consoleOutputLinkStyle
Added test for default value
Add test for simple Build Flow job.
Merge pull request #144 from benpatterson/master

[JENKINS-16364] Add support for Build Dsl job type.
Addressed peer review comments
added comment
Support setting boolean value for changeBuildStatus property of Jacoco code coverage plugin
Merge pull request #164 from kmarquardsen/BuildPipelineView

Added missing options for the BuildPipelineView
default to true for changeBuildStatus's boolean param so that calling the method with no args will set the value to true
If the user doesn't explicitly set changeBuildStatus value, don't write it out to the XML.
Add test for argument variant for changeBuildStatus
added iterable for whitelist
Releasing 1.21
Bumping to next rev