Add --bundle,-dab flag for specifying dab file

[janetkuo]

Now we can specify a dab file with --bundle or -dab:

$ kompose convert --bundle=docker-compose-bundle.dsb 
file "redis-svc.json" created
file "web-svc.json" created
file "redis-deployment.json" created
file "web-deployment.json" created

--bundle can't be used with --file:

$ kompose convert --bundle=docker-compose-bundle.dsb --file=docker-gitlab.yml
FATA[0000] Error: compose file and dab file cannot be specified at the same time

Fixes #53

[janetkuo]

I add another commit for copying bundle file names for charts