Refactor: renamed AddServerActivity fields
Material design: removed unecessary labels.

Labels were removed, some of them were replaced by hints.
Using the actionbar to confirm/cancel add server.

Using material design icons.
Refactor: using hash to determine sensor icon.

Several optimization on code readability.
Refactor: Using enum to indicate severity.

Using enum instead of magic constants to indicate severity.
Removed unused strings.
Created styles for EditText