Verify that a whitelisted address is not also blacklisted

[rjl]

From Matthew Jonkman:

A verification that they're not blacklisting something that's already whitelisted. Just to avoid conflicts and confusion.

[dmorton]

Added better reporting in [532]. The only way I can see to do better is to either list every address changed, or to add a javascript warning before submitting. Comments?

[jleaver]

Java script is difficult as there are compatibility issues with browsers. The alternative is to return an error instead of updating the the formerly white or black listed item. However, I kind of like the way it works now.