Implement task defaults based off of collection settings

[Matt McManus]

ie: let me set a cwd on a collection and any task in that collection will have that setting if if they don't specify it

ummon.defaults['rc4'] = { cwd: '/websites/staging.waytohealth.org/project/versions/rc4' }
ummon.tasks['rc4.processData'] = { command: 'echo awesome'... }
ummon.showTask('rc4.processData') //  { cwd: '/websites/staging.waytohealth.org/project/versions/rc4', command: 'echo awesome' ...}