Set default maximum viewing range to a bit more than default server send range to make fog work well

Defaults modified from original: alpha=200, key=F10

Set default maximum viewing range to a bit more than default server send range to make fog work well

Remove stuff made obsolete by making players more ActiveObject-like and raise protocol version number by one (because it is not compatible at all anymore)

occlusion culling fix, a little reshaping of map rendering for more useful profiler output and dynamic profiler text size

Default max_simultaneous_block_sends_server_total to 2 to make network not cough too much on the fixed block sending code

strict_protocol_version_checking setting; PROTOCOL_VERSION in clientserver.h; clean up defaultsettings.cpp and minetest.conf.example