Dan raised the comment in the previous patch set that it doesn't make
sense to provide two options and four states when there are really only
two possibilities; install the jre or the jdk.
This change removes the jdk and jre class parameters and replaces them
with a single distribution parameters.
Anonymous arrays and comparing booleans does not work in 2.6.8 like they
do in master. In 2.6.8 we cannot compare a true / false variable to a
string inside of Ruby without forcing the function argument to be a
string.
