Allow remote debugging to be enabled

[rstjohn]

add an overridable property to allow us to enable remote debugging. Concretely, in the bootstrap.conf file the following change could be made:

# Enable Remote Debugging
{% if nifi_enable_remote_debugging -%}
java.arg.debug=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8000
{% else -%}
#java.arg.debug=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8000
{% endif -%}

[tcirner]

could you clean that up a little bit?

[tequalsme]

Merged to develop May 16th