Add version fields to manifest (#189)
Add version fields to manifest (#189)

`addDefaultImplementationEntries` field of the jar plugin adds the following three fields:

```
Implementation-Title: Google Cloud Spanner Dialect for Hibernate ORM
Implementation-Version: 1.2.0-SNAPSHOT
Implementation-Vendor: Google LLC
```

Fixes #187 
GoogleCloudPlatform/google-cloud-spanner-hibernate,GoogleCloudPlatform/google-cloud-spanner-hibernate,GoogleCloudPlatform/google-cloud-spanner-hibernate