Text Finder Plugin

This pull request adds support for Jenkins Text Finder plugin.

```groovy
job {
    ...
    publishers {
        ....
        textFinder(String regularExpression, String fileSet = '', boolean alsoCheckConsoleOutput = false, boolean succeedIfFound = false, unstableIfFound = false)
    }
}
```

Example:

```groovy
job {
    ...
    publishers {
        ...
        textFinder(/\[ERROR\]/, '**/*.log', false, false, true)
    }
}
```