Revert "Remove unreachable code"

This reverts commit 39615669c44a52bf54c4c411c7aeeca21144955b.
streamer: Reenable annotation event streaming
features: Add a simple feature flag harness

This commit adds a relatively simple feature flag harness which allows
us to query the activation or otherwise of named features when handling
requests.
Add unicode normalization for page search
Unicode normalization for stream backend
Unicode normalization for ES
Unit test for string-helpers
Unit tests for FilterToElasticFilter
Get rid of normalize parameter

We judge whether to normalize or not by the variable type
Match query for stream searches

Old default was term query.
Removed es options from client-side field definitions.
Cleanup old code
Remove case-sensitive flag from filter schema

We do everything case-insensitive, that flag is no longer needed
Do not normalize searchfilter sent to the backend.

We have every analyzers setup for ES to do that more precisely.
Change asciifolding to icu_folding
Rename unidecode function to uni_fold
Remove all marks with stringHelper

- Using proper regexp from xregexp
- Renamed unidecode to uniFold

Thanks for @nickstenning
Move streamer test to h/test
Remove normalization parameter from uniFold
Simplify too complex function in streamer.py

FilterHandler.evaluate_clause had a case_sensitive remnant, removed
FilterToElasticFilter.conver_clauses was dissected by es query_types
Add more tests for stringHelper
streamer: Put streamer behind a feature flag

Only enable the "realtime" features if the "streamer" feature flag is
enabled.