core: add output/detail methods to Ui, prefix with arrows
core: colorize VM output for each VM in a command
core: align text and make sure its all lined up with prefixes
providers/virtualbox: many `detail` level output
providers/virtualbox: more detailed output
Fix tests for new UI methods
core: convert more output to `output` method
core: Ui color should be red on errors, yellow on warnings
core: extensive tests for Vagrant::UI classes