Refactor Actions for 0.2.x

[danbradham]

Proposal

Implement a simplified Action class.

class Action(object):
    description = ''
    identifier = ''
    label = ''
    menu = ''
    icon = ''

    def is_available(self, ctx):
        '''Return True if the action is available in the given context.'''
        return True

    def parameters(self, ctx):
        '''Return a Cerberus Schema dict to validate arguments passed to `Action.run`.'''
        return True

    def run(self, *args, **kwargs):
        '''The Actions main execution method.'''

Motivation

Make it easier to add custom menu items and actions.