Extract preview dependency logic?

[LinqLover]

At the moment, TelegramSmalltalkBot as well as TelegramBot and SimulationStudio and some pieces of logic for installing preview dependencies in their baseline which are partially overlapping. Because they contain common logic that needed to be synced manually between all repositories, it might be worth a thought to extract this logic into a central place, i.e. another repository that would work as some kind of Metacello extension.

Since the general approach of these dependencies is questionary, this should be reconsidered.
Problems with the current approach include:

• uninstallability
• cacheability (see also Accelerate updates #14)
• selectivity (at the moment, one method is required for every group of prevdeps)

For a general discussion, also see the comments in LinqLover/TelegramBot#1 as well as Metacello/metacello#528 and Metacello/metacello#530.