Clarify the difference between Hadoop and Accumulo native libs in bootstrap_config.sh script

Lindsey Kruper on serverfault expressed some confusion in bootstrap_config.sh's warning messages in http://serverfault.com/questions/790154/what-should-hadoop-prefix-be-for-accumulo-installation/790255

Rightfully so, the script's warnings don't differentiate between what is a Hadoop setup issue and what is Accumulo setup.

We can easily improve this with better error messages.