Always use ThisBuild version for sonatypeBundleDirectory (#199)
Always use ThisBuild version for sonatypeBundleDirectory (#199)

Changes `sonatypeBundleDirectory` to always use the version directory of the root project.

Before:

```
sbt:mutation-testing-metrics-scala> version
[info] module-a / version
[info]  1.4.1
[info] module-b / version
[info]  1.4.0
[info] version
[info]  1.4.0
sbt:mutation-testing-metrics-scala> sonatypeBundleDirectory
[info] module-a / sonatypeBundleDirectory
[info]  /root/target/sonatype-staging/1.4.1
[info] module-b / sonatypeBundleDirectory
[info]  /root/target/sonatype-staging/1.4.0
[info] sonatypeBundleDirectory
[info]  /root/target/sonatype-staging/1.4.0
```

After:

```
sbt:root> version
[info] module-a / version
[info]  1.4.1
[info] module-b / version
[info]  1.4.0
[info] version
[info]  1.4.0
sbt:root> sonatypeBundleDirectory
[info] module-a / sonatypeBundleDirectory
[info]  /root/target/sonatype-staging/1.4.0
[info] module-b / sonatypeBundleDirectory
[info]  /root/target/sonatype-staging/1.4.0
[info] sonatypeBundleDirectory
[info]  /root/target/sonatype-staging/1.4.0
```
xerial/sbt-sonatype