Update sv_plugin.lua

Added a config option for resetting the player's position after exiting observer mode.
Update sh_plugin.lua

Include new cl_plugin for adding the config option.
Create cl_plugin.lua

ObserverReset config option added.
Merge branch 'master' of https://github.com/SomeSortOfDuck/Clockwork
Added SomeSortOfDuck's observer_reset config option.