Replace some LWRPs with definitions

The definitions run a ruby_block at compile_time to make sure that
the template[/etc/burp/burp.conf] will have an up-to date includes/excludes list
at the converge phase.

To use in a recipe:
burp_include '/var/lib/mysoft'
burp_exclude '/var/excludeme'
burp_exclude_regex '^myregex.*'

those definitions should be used instead of the corresponding node['burp']
attributes to avoid weird isssues because of the order of elements in the
run_list.

I'm trashing the idea of multiple clients on a node for now.
(the burp_client LWRP)

*The lazy block in providers/client.rb requires Chef >= 11.6*