Removed /obj/effect/begin and /obj/effect/laser. Both were unused.
Updated chem grenades. They use assembly holders instead of snowflake code for each assembly.
The build process is much the same, except they require an igniter-X assembly instead of a single assembly item. You can also just use a cable coil to get regular grenade behaviour.

Updated the changelog.
Removed var/special_assembly from assembly_holder as it was unused.
Updated singletank bombs to pass hear_talk to their assembly.