Isis Visual Update

### Attempt to modernize the admin template Isis

Joomla 3.x was released on Thursday, 27 September 2012. Thats 2 years already now! Although through these months many visual cues were added to the Isis template the look and feel is almost identical. This update tries to modernize it but, at least in my eyes, without alienating it.

##### What’s different:
Buttons, gone the gradients, primary follows the main color of the links and now have some nice transitions
navbar, header are now unified in solid color
chosen has its own less file and now uses IcoMoon font
Calendar has a new css
Login has a new layout override for bigger button and an hr above that button

There is an easter egg: first and second font selector (document wide) is Ubuntu Thin and Ubuntu which if the users got it in theirs computers is gonna be used. Get it here: http://font.ubuntu.com/about/

I prepared a short screen cast moving around to demonstrate it, you can watch it here: https://www.dropbox.com/s/oz4q6gq4yb6zio5/isis-demo.mp4?dl=0

And some photos:
![screenshot 2014-09-14 23 10 42](https://cloud.githubusercontent.com/assets/3889375/4265327/57d3e086-3c4b-11e4-8b42-0cb43bc8e74f.png)
![screenshot 2014-09-14 23 10 15](https://cloud.githubusercontent.com/assets/3889375/4265328/5a71bfca-3c4b-11e4-8648-05e58d4b7ae4.png)
![screenshot 2014-09-14 23 09 42](https://cloud.githubusercontent.com/assets/3889375/4265329/632d2992-3c4b-11e4-9319-bba233b0a666.png)
![screenshot 2014-09-14 23 09 16](https://cloud.githubusercontent.com/assets/3889375/4265331/68538010-3c4b-11e4-8e22-a1d78d6c199b.png)

Comments and tests are welcome as usual