[2.1.8] Stack inserters not possible without rocket capacity spam in tooltips

[SWeini]

Stack inserters are currently guarded by the space_travel feature flag, so it is not possible to have those juicy inserters or mining drills without each and every item having the rocket capacity in the tooltip. space_travel should not include random things, there is a new expansion feature flag for it. You could also use the existence of any feature flag for small things such as belt stacking.

P.S.:
There are other things guarded by space_travel that don't make any sense, probably best to check them all
- agricultural towers (non-planet mods might want to use them)
- lightning and corresponding buildings (maybe, you could argue no one wants lightning on nauvis)
- spoilage controls in advanced tab of map generation (just a bug)

[boskid]

I am not considering this to be a bug report, however i will consider this as a modding interface request. For 2.1.9 i made belt stacking (inserter + loader + mining drills) enabled when either `expansion` or `space-travel` flag is set. First flag is main one, second is for compatibility.