feat: refurbish bottles

[bahrmichael]

This PR introduces a mechanic to return dirty bottles that players can refurbish into new bottles.

Bottles are returned to Bottle Return Stations with a mechanism similar to the city debt for treasuries.

Players can then use the recipe "clean bottles" or "clean bottles with soap" to get regular bottles again.

Todos:

• ~[ ] Notify the player via a one-time message that dirty bottles are returned in the markets. This is a new mechanic and may clog up the markets.~
• [x] Introduce bottle return entity where citizens return dirty bottles.
• ~[ ] Consider refurbishment plants instead of letting players refurbish bottles in assembling machines.~ I felt like mandatory plants are not a good fit yet, and would rather let the player build the recycling setups themselves. Will reconsider larger plants for boosted production, e.g. steel mills.

[winex]

i think returning to markets is not a good idea -- that will block them 100%. yeah, mixing input/output is always wrong. didn't you think about some new garbage-piling entity? or add market-option (as checkbox, similar to Enable/Disable) to use as city output (might be harder?)

+we could use it on any future additions

[bahrmichael]

i think returning to markets is not a good idea -- that will block them 100%. yeah, mixing input/output is always wrong. didn't you think about some new garbage-piling entity?

Thought about it, and am leaning towards a dedicated entity now. Had a similar problem with train stations, where I introduced GUI settings to filter passengers. Here it's more reasonable to introduce a new entity.