User will be asked to give user & port if key association fails.

In this commit:
- Created popup for user & port input
- Created popup triggering on key association fail
- Pass user and port via ajax
specify user/port on the backend for ssh-ing
Changed SSH User and Port Popup Style, also

- Added a message that shows previous user and port fail
- Moved inline css to a css file
- Changed a little bit the way we handle the popup and its data
Merge branch 'ssh_userPort' of github.com:mistio/mist.io into ssh_userPort

Conflicts:
	src/mist/io/static/js/app/controllers/keys.js
pass no username if not specified
specify port on backend add, bare metal
fix add bare metal backend ssh prot
Remove some redundant code
Rename "thirdFiled" to "Port" when adding bare metal backend
add ssh port on bare metal machine
Merge pull request #106 from mistio/ssh_userPort

custom ssh user and port