Integrate with i18n_variable

Unfortunately, whilst the patch may give fallback to variables, the mere presence of the i18n_variable+variable_realm modules breaks the interface string fallbacks that Language Hierarchy provides! Patch to follow in the next week...

Here's an updated patch that improves the above issue. The only way to do it within Language Hierarchy itself is to have a low enough module weight so that it acts before i18n_variable on hook_language_init(). However, there are still rogue calls to t() during bootstrap / language initialization that cause problems though, which I'll raise issues against variable module to resolve, since there are cases that cannot be solved within Language Hierarchy (e.g. getting translations for languages other than the current interface language).

Sorry, I missed a file.

Oh dear, it gets worse... unfortunately language hierarchy needs to act before i18n_variable for hook_language_init(), but after it for hook_variable_realm_info(), so the changing the module weight isn't sufficient. New approach on the way...

Right, here we go, hopefully the last attempt! Good job we have a client that is / will be testing this :-)

I've added a new submodule for integration with i18n_variable, since there are submodules in use for interacting with other i18n/translation modules. The bonus of this is that the base Language Hierarchy module, which needs to act before i18n_variable, can be set to a low enough weight, whilst the submodule can keep a higher weight so it can act after i18n_variable.

And another attempt... this one allows for values from different stores to be accessed within the same page request.

Here's a version with tests ... however it depends on the test module added in #2596321-9: Empty node titles in content overview (which is why it's guaranteed to fail!).

I don't have time right now to produce a patch with just the tests either, sorry.

Committed!

Sorry, I misunderstood how testbot would interact with issue status. The test failed because the patch had already been committed! (The test had passed beforehand)