[JENKINS-18583] - Refactoring of PerforceSCM to remove newInstance()

This change removes need in newInstance() handler and also provides classes for future refactoring.
In addition, the change adds instance IDs to config.jelly, therefore there won't be conflicts between radioButtons().
Resolves https://issues.jenkins-ci.org/browse/JENKINS-18583

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Merge branch 'master' into multiple-scm-instatination-fix

Conflicts:
	src/main/java/hudson/plugins/perforce/PerforceSCM.java

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Merge pull request #33 from jenkinsci/multiple-scm-instatination-fix

[IN_PROGRESS][JENKINS-18583] - Fixed PerforceSCM instatination forn Multiple SCMs