added clone timeout option for Git SCM, fixed JENKINS-25525
Merge branch 'JENKINS-25525'
Fix `copyArtifact`

The `copyArtifact` step is currently broken for matrix projects. The reason for this is that the presence of the `projectName` attributes triggers the `CopyArtifact` plugin to behave differently, as demonstrated below:

```
private boolean upgradeIfNecessary(AbstractProject<?,?> job) throws IOException {
    if (isUpgradeNeeded()) {
        int i = projectName.lastIndexOf('/');
        if (i != -1 && projectName.indexOf('=', i) != -1 && /* not matrix */Jenkins.getInstance().getItem(projectName, job.getParent(), Job.class) == null) {
            project = projectName.substring(0, i);
            parameters = projectName.substring(i + 1);
        } else {
            project = projectName;
            parameters = null;
        }
        LOGGER.log(Level.INFO, "Split {0} into {1} with parameters {2}", new Object[] {projectName, project, parameters});
        projectName = null;
        job.save();
        return true;
    } else {
        return false;
    }
}
```
minimum required version of copyartifact plugin is 1.26
Merge branch 'copyartifact'
moved Context and ContextHelper to javaposse.jobdsl.dsl
better JavaDoc
[FIXED JENKINS-26071] Extend HtmlPublisher for configuration of allowMissing
[JENKINS-25482] Support for extended email triggers Always, FirstUnstable, FixedUnhealthy, SecondFailure, StatusChanged
cleanup
Merge branch 'ext-email'
Add ConcurrentModificationException workaround.
Merge pull request #336 from CoreMedia/context

Moved Context and ContextHelper to javaposse.jobdsl.dsl
Allow views to be deleted
Separate remove actions for jobs and views
Consider views in folders
added Troubleshooting section, changed some wording
Merge branch 'concurrentmodificationexception'
added closure for HTML report details
Merge branch 'JENKINS-26071'

Conflicts:
	job-dsl-core/src/main/groovy/javaposse/jobdsl/dsl/helpers/publisher/HtmlReportContext.groovy