Feature cura config

Added functionality to set a directory holding cura profiles.
Added functionality to select a cura profile via selectbox.
Added functionality to edit cura profile ini's via the settings.
Added functionality to copy cura config profiles.

Should resolve request https://github.com/foosel/OctoPrint/issues/477

Basic settings:
![octoprint_cura_basic_1](https://cloud.githubusercontent.com/assets/978192/3769956/619b7752-18e5-11e4-8256-92ee72481d43.png)
![octoprint_cura_basic_2](https://cloud.githubusercontent.com/assets/978192/3769957/619fdba8-18e5-11e4-9443-b44952cc0786.png)
![octoprint_cura_basic_3](https://cloud.githubusercontent.com/assets/978192/3769958/61a329f2-18e5-11e4-9f16-ddbb75e8dbca.png)

Advanced settings:
![octoprint_cura_advanced](https://cloud.githubusercontent.com/assets/978192/3769959/61a69d1c-18e5-11e4-89de-5c0e3b8124af.png)