See this discussion on wikitech-l: https://lists.wikimedia.org/pipermail/wikitech-l/2015-October/083797.html
In short, extension.json has a 'requires' section where you can specify required MediaWiki core versions for an extension. It would be great if this section could be expanded to include 3rd party extensions, to handle cases where a 3rd party extension depends on another (for example, VikiSemanticTitle and VikiTitleIcon are plugins to the VIKI extension, and thus require VIKI to be installed).