Allowing plugin shells to be called without plugin notation

Plugin shells will not require a plugin notation prefix anynmore
given that there are no shell name conflicts
Adding tests for plugin shell auto aliasing
Fixed CS error
Udating completion shell tests
Logging shell aliasing conflicts
Adding a scope to shell dispatcher logging messages
Merge pull request #4595 from cakephp/3.0-plugin-shell-aliases

3.0 plugin shell aliases