Added help for the SharedDirectoryInstaller according to Jesse Glick's comment
URL:
https://github.com/jenkinsci/extra-tool-installers-plugin/commit/70ad1fa728c2c353d4f6baf9836ba86d40a43ebe#commitcomment-3687460

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Added support classes for variables substitution

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Added getters to the installer

Signed off by Oleg Nenashev <nenashev@synopsys.com>
Added substitution of global and node variables.

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Merge pull request #1 from synopsys-arc-oss/variables_support

Variables support
[maven-release-plugin] prepare release extra-tool-installers-0.2
[maven-release-plugin] prepare for next development iteration