Support role files

Transfering roles directory and write path configration to solo.rb.
Add feature: Chef roles auto discovery

Chef roles auto discovery appends roles of chef to run_list of each server.
This feature makes name-based relations with role of capistrano and chef's one::
- Discovering role definitions of chef from role-names of capistrano that server is assigned
- Run chef with discovered roles at each server
- Be able to play different roles of chef for each server
Merge branch 'chef_roles_auto_discovery' into integrated