merge with OC-9012 (local)
store relative plugin paths in v6_dependency_solver
run v6 plugins with Ohai::System#all_plugins, add deprecation message
add ability to run v6 plugins with Ohai::System#run_plugins
move #provides to specific plugin version class
Ohai::System#all_plugins executes #load_plugins, #run_plugins
log error to debug
Merge pull request #192 from opscode/OC-9362

Add ability to run v6 plugins