Support Apollo 2 / Vulcan 1.13

[eric-burel]

Replaces #20. Ungoing update to Apollo2 / Vulcan 1.13

Hopefully those updates should allow some code simplification, however there are many breaking changes. I've got a non-buggy workflow but still not working as expected.

Edit: it seems to work ok actually, now I need to update the UI. Updates seems to create new files all the time, and removal does not seem to be triggered, I'll also try to fix this.

Edit 2: @ochicf it now works OK in my app with no breaking change. Vulcan needs this PR to be merged for this new version to work, it enhance the Apollo 2 server to allow file upload with the new API. I hope to merge it within a few days.

Also handlers now correctly remove stale files when you replace or delete a file.

I've also modified the UI a bit to make it more replaceable. I uses similar patterns as the ones we are progressively introducing in the core to allow replacement of core components without rewriting their logic. It's a bit verbose but it seems to do the trick, I've managed to create a Material UI input.

Only thing I did not test is multiple file upload. I've updated the code but I am not 100% it will run as expected, to be tested. Also filecheck is ran client side but not server side, that's something I also hope too tackle soon because it's necessary to have a secure system. Eventually, a few file might be deleted but I was not 100% sure (eg https://github.com/OrigenStudio/vulcan-files/blob/master/lib/client/interface.js), since now apollo-upload-client does the heavy lifting client side.

The PR merges to the develop branch, however it may be better to create an apollo2 branch to support both legacy Vulcan apps and new Vulcan apps (> 1.13)?