use a local storage for chat history which prevents mix ups in netgame and simplifies code

less cryptic text insertion

gather a few common code

implement up and down keys to navigate in the chat history, needs testing over network

don't display squares when pressing arrow keys in chat

formatting

do not hardcode CMAKE_INSTALL_PREFIX for windows, but rather put it in the script, so that custom build setups still work

Hard math to fix issue #571. Well, not really hard math, just checking if vector is in opposite direction and trait that as a special case when removing rope dividing point (this could only happens when rope sticks to land outline, so this basically fixes a bug in another bug).

oups

fix compilation with clang. fixes issue #553 - thanks to julien for reporting and to drew for the first part of the fix