Add EC2 credentials CRUD

ec2 credentials: create, delete, list, show

Change-Id: I82ff84ed433cd9a2da9534bf5f584a2e1a3fe68c
Update documentation with info about setup.cfg

Change-Id: If87df1e6415d0b70b6605b1d89eda639fc44a0b6
Merge "Add EC2 credentials CRUD"