WIP Normalize for diacritics

PR branch for #729

Tasks to do
- [x] unicode normalization client side for page search with unorm and xregexp
- [x] unicode normalization for ES queries, setting up analyzers
- [x] unicode normalization for backend stream
- [x] add tests
- [ ] launch a showcase dokku instance 
I'm not sure I like this test. It's testing the internal implementation details of `FilterToElasticFilter` rather than its behaviour. Could you find a way to test the return value rather than mocking out the static `equals` method?