Add Ldaptive support for Relay staff attributes

@frett 

Note this PR already includes the changes from https://github.com/GlobalTechnology/idm-user-management/pull/6
google guava has a toStringHelper[1]. I haven't used it before, but it might help clean this function up a bit.

I saw a tutorial on how to configure IntelliJ to do code generation for it [2], so don't worry about changing it at the moment, I can probably generate it in under a minute.

[1] https://code.google.com/p/guava-libraries/wiki/CommonObjectUtilitiesExplained#toString
[2] http://www.jworks.nl/2013/01/10/generate-a-tostring-using-guava-objects-tostringhelper-with-intellij/