Add improved splitting utility

[bennothommo]

Adds a much faster and more robust subsplit utility into Winter CMS, and adds a winter:split command to be used by the maintainers to execute a subsplit of the modules into their split repositories.

Usage:

Description:
  Runs a subsplit to publish the Winter CMS modules in their own repositories.

Usage:
  winter:split [options] [--] <token>

Arguments:
  token                                GitHub token for writing to the repositories.

Options:
  -b, --branch[=BRANCH]                Publishes a branch in the subsplit repositories.
  -g, --git[=GIT]                      The path to the "git" binary.
      --remove-branch[=REMOVE-BRANCH]  Removes a branch in the subsplit repositories.
      --remove-tag[=REMOVE-TAG]        Removes a tag in the subsplit repositories.
  -s, --sync                           Fully synchronises branches and tags with the subsplit repositories.
  -a, --tag[=TAG]                      Publishes a tag in the subsplit repositories.
  -w, --work-repo[=WORK-REPO]          Defines the location of the working repository. Defaults to "/storage/temp/split-repo" within the base path.
  -h, --help                           Display this help message
  -q, --quiet                          Do not output any message
  -V, --version                        Display this application version
      --ansi                           Force ANSI output
      --no-ansi                        Disable ANSI output
  -n, --no-interaction                 Do not ask any interactive question
      --env[=ENV]                      The environment the command should run under
  -v|vv|vvv, --verbose                 Increase the verbosity of messages: 1 for normal output, 2 for more verbose output and 3 for debug

It should be run as follows:

php artisan winter:split <github token>

and followed by one of the following:

• -s|--sync: Runs a full sync of all branches from the main repo to the subsplits
• -b|--branch <branch>: Runs a sync for a single branch
• -a|--tag <tag>: Runs a sync for a single tag
• --remove-branch <branch>: Removes a single branch from the subsplits
• --remove-tag <tag>: Removes a single tag from the subsplits

[bennothommo]

Moving work to the https://github.com/wintercms/cli - the maintainers feel this is too "internal" to be used within the CMS itself.