Add Java MongoDB read/write pipelines

[Amar3tto]

Pipelines added:

1. Write to MongoDB
   IO: MongoDB IO
   SDK Language: Java
   Run instruction:

• Start MongoDB
• Create collection and fill with test data
• run java WriteMongoDB --runner="DataflowRunner" --project="your-project" --region="your-region" uri="your-uri" --dbName="your-db-name" --collection="your-collection"

2. Read from MongoDB
   IO: MongoDB IO
   SDK Language: Java
   Run instruction:

• Start MongoDB
• Create collection and fill with test data
• run java ReadMongoDB --runner="DataflowRunner" --project="your-project" --region="your-region" uri="your-uri" --dbName="your-db-name" --collection="your-collection"

[Abacn]

please add bson and beam-io-mongodb to pom.xml as dependency. Currently it works because beam-sdks-java-extensions-sql depends on beam-sdks-java-io-mongodb. But in general we should explicitly add the dependency that directly used.