[FIXED JENKINS-19905] - Removed section from rebuild options, added help.

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
[JENKINS-19910] added support for maven metadata plugin
[JENKINS-19843] Provides an extension point for other plugins to support rebuild plugin.
[JENKINS-19910] added support for maven metadata plugin
[JENKINS-19843] Removed setters frpm RebuildParameterPage. Developers set its properties with the constructor.
[JENKINS-19843] Add an instruction to add a dependency to rebuild plugin to pom.xml.
Merge pull request #17 from ikedam/feature/JENKINS-19843_RebuildParameterProvider

[JENKINS-19843] Provides an extension point for other plugins to support rebuild plugin.
Merge pull request #15 from synopsys-arc-oss/rebuild-ui-fix

[FIXED JENKINS-19905] - Removed section from rebuild options, added help...
Merge pull request #16 from hrmohr/JENKINS-19910

[JENKINS-19910] added support for maven metadata plugin
[maven-release-plugin] prepare release rebuild-1.21
[maven-release-plugin] prepare for next development iteration
Revert "Fix proposal for [JENKINS-20288] - Allow rebuild plugin to use default configuration page from any parameters."

This reverts commit d412c3d4224af25d35ea07c0f6cb68149afb9ffe.
Merge https://github.com/jenkinsci/rebuild-plugin
Fix proposal for [JENKINS-20288] - Allow rebuild plugin to use default
configuration page from any parameters as last resort option.
If no RebuildParameterProvider, nor internal suitable jelly file is
found, then it falls back onto default parameter value page.