Improve web socket example layout
Improve web socket example layout

On iOS the input grew as wide as the input text and the send button
filled the rest of the space. Set a fixed size on the button to ensure
consistent layout among both platforms.

Center both button and input vertically in a container with a fixed
height, so that they appear in one line.

Change-Id: I49e7dff2edee1b3acd16a293298217b3765143b5

eclipsesource/tabris-js,eclipsesource/tabris-js,eclipsesource/tabris-js