initial work on screen text

Screen text is positioned in screen coordinates and therefore in 2D.
This means it will not move with the camera.

Change-Id: I3cf2e8859871ebc8034396b4c2d6f1ff9fe5d9f6
let us not implement this large constructor in the header file

Change-Id: I271882d8cba0201b6aa63308e502509b3c2ac170
remove unused method and shader

Change-Id: Ic4aafe0aa596f97ea4220e6fc063a61fa13b877d
remove more unused methods

Change-Id: If50cb8b21aa7b7196027a411f207eff9aee3676a
add initial work on zoom into the bar movement

Change-Id: Idc8c1f27dbeafdf34706f09c890f202849c2ce33
adapt bar size to demo

Change-Id: Id746ce00f9e91397a3edf0b39bf7dbb08ea59885
block user input while we are in another user interaction

Change-Id: I25a846b0648d2d28585a58066a9bb1088d607c24
improve screen text positioning

Change-Id: Ia1f4ae40b8dbed2324c600f7ef68a33a5b04027b
remove unnecessary debug message

Change-Id: I63e65bce671d1feab4ea93bdff906b597ce180c3
react only to left mouse click

Change-Id: Ia4c2c52b8803cd36d7ed32be559ba446589377e7