Make protobuf directories consistent

[chbatey]

Ideally all build tools could pick up from proto (standard for java tooling) and protobuf (scalapb). If not make build tools consistent so SBT protobuf regardless of language and Gradle/Maven proto regardless of language and override defaults in sample projects so they work with all 3 build tools

[jrudolph]

Is this now closed? And what was the final decision which directories to show by default? If we chose to use proto everywhere we might want to adapt it in the Scala documentation.

[ktoso]

Suggestion was to:

• support both - done
• show docs consistent with what given build tool likes - not sure if done, please confirm @chbatey @raboof ?

[chbatey]

We should do a check of the docs then close this.

[raboof]

checking