Move configuration properties prefix to a dedicated namespace

[snicoll]

Thank you for your work on the starter. As documented in the reference guide we prefer that third party starters do not use our configuration namespace.

Can you please rename those spring.data.arangodb.* in ArangoProperties? A root arangodb.* sounds good.

Thanks!

[rashtao]

@snicoll thanks for pointing this out!
fixed in 4cfa6fd