Merge implementations of AbstractCellInventory(Handler) and make them channel agnostic.
This breaks API, but makes it a LOT easier for addons in the long run.
Also adds some convenience API methods.
…torageCell and IStorageChannel
SonarQube analysis reported 89 issues
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Note: The following issues were found on lines that were not modified in the pull request. Because these issues can't be reported as line comments, they are summarized here: