add ToolInstallation support
config gui
TODO: add auto installer
add auto installer
Merge pull request #7 from wolfg1969/feature/sbt_installation

added ToolInstallation support according [#JENKINS-15824](https://issues.jenkins-ci.org/browse/JENKINS-15824?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel)
allow empty path input
autoinstaller worked
Merge pull request #8 from wolfg1969/feature/sbt_installation

auto installer worked