Add example for adding custom behaviour to all repositories.

[thomasdarimont]

We should add an example that demonstrates this.

[odrotbohm]

:+1: I'm in the finishing steps for DATACMNS-542, which should significantly ease this. There's already a feature branch with a pretty complete implementation of this. Feel free to use this to spike an example.

[odrotbohm]

Trying to find the missing test cases for the JPA feature branch I discovered that there's a branch here to solve #73, which is basically a duplicate of this one. I'll reopen it as it apparently hasn't been merged into master yet (pending completion of the improvements in Spring Data Commons / JPA).

[thomasdarimont]

Alright :)

[mp911de]

Fixed via b8e2943