Added world model overrides to ItemDefinition based on stack size, so we can use different world models for different stack sizes
Should be arranged in descending order, so smallest stack size -> largest
Initial support for triggering NPC conversations via phone
Required PhoneController refactors
Added OnFlagsChanged, ServerInit, PostServerLoad, DoServerDestroy, Save and Load callbacks to EntityComponentBase (this removes a lot of duplicate boilerplate on MobilePhone and Telephone scripts)
Added Tags support to BaseItem. Added "drone" tag to all drone unit definitions. Added SpeedModifierTech and HealthIncreaseTech. Added Aerodynamics and Graphite Armor techs to the Drone Hub.
Merge branch 'master' of sbox-rts