Manage github / gitlab configs in epinio

[richard-cox]

Users should be able to list, create, edit, delete git credentials

• Create a new git config resource, including model
• Create a new side menu item that shows these resources
• Create edit component to create / edit resource
  • Inputs to reflect config resource
  • User should select type (github, gitlab, hosted github, hosted gitlab)
  • User should supply a token (we should include info on how to find / create one in both github and gitlab)
  • If hosted, user must supply a url