[FEATURE] Add option "allowedBranches" and variables in filename to PackageBuild plugin

We had the problem that each commit in any branch creates a package. This creates a lot of waste we don't need. We just want packages of the master and develop branch. So with this option you are able to restrict this plugin to the given branches. The option expects an regular expression like this: 

```
  PackageBuild:
    directory: "/.../builds/%project.title%/%build.branch%/"
    filename: "build-%build.id%"
    allowedBranches: "^master$|^develop$"
    format: tar
```

Furthermore now the filename may also contain variables, which become replaced.