multiple target and multiple targetnames per entity support

original code and concept by ==Troy==, rewritten by /dev/humancontroller
ported c1c289d, 6018f9b and cb52adc to unvanquished by Tim
adapt function and variable naming and add some documentation
start entities definion file cleanup with a skeleton
add cleaned up status-quo of the worldspawn to entitiy definition and g_spawn
add cleaned entity definition and documentation for one of each major entitiy groups
target_position, path_corner, and trigger_always
remove the idtech4-entity-definition format again, since it seems to produce parseproblems
daemonmap->Q3MAP2; +func_group; general cleanup
Merge branches 'master' and 'feature/multitarget' into entities
add target_relay to entity def and update all already ported entitiesdefs to reflect multitarget and multitargetname functionality
port and correct team_* (buildables and startingpoint) as well as light entities in the definition file
port func_timer and rename functionnames in g_trigger already to trigger_timer (without changing the classname yet to remain compatible)
rename func_timer to trigger_timer, since it was an trigger all along, but keep func_timer as backward compatible classname-alias
trigger_timer will warn with a deprecation message if func_timer was used to reference to it
update documentation accordingly
port target_speaker over to new entity definition file
merge target_delay into target_relay (in a backward compatible way)
abstract function to set deprecation classname alias and warn about it, since we probably gonna use it a lot more
Merge branch 'master' into entities
cleanup everything around info_null and info_notnull (also warn about deprecated usage here)
deprecate misc_teleporter_dest in favour of target_position, and pull intermission entities a little bit closer together
small change on how to handle deprecated entity classnames to simplify code with increase in deprecations
apply small collection of minor cleanup-refactorings

rename datatype ANGLEHACK into yaw, switch minus to em dash and rename an earlier introduced function name into something more consistent