Remove obsolete file
Reduce SQL queries to generate column names #2340
Remove unused code to export world #2340

Exporting world was needed to prototype map. But the code is now
obsolete and should use aggregator instead. Futhermore /api/table/country
should now be flexible enough to export the world or/and all countries.
Column acronyms should keep symbols
Speed up population fetching by avoiding hydrating objects #2340

/api/table/country get a significant increase in speed
Add aggregated geoname to benchmark #2340
Everything using JSON file for test should be in ApiComputing group #2340
Prevent wrongly duplicated cache key #2340

Since spl_object_hash() recycle hash from destroyed objects, it was
possible to get the same cache key for two different objects, if the
first one was destroyed in between. This resulted in changing results
for end-users depending on what he asked for (what filters).

We now ensure that object used in cache key are never destroyed by
the garbage collector, by simply keeping a reference locally. This will
increase memory consumption though.
Introduce persistent cache key for incoming persistent cache #2340

Persistent cache key rely on model ID from database instead of
object's hashes. This allow us to persist cache key between two
different PHP process.

Also this correct a bug of cache were the key generated wrongly included
the collection of already used formulas. This did not make sense and lead
to wrong results in some very rare cases. Those mistakes were not noticed
until now because it was for Other Improved for which we do not have any
values from original Excel files.
Support array indices for cache key #2340

For AbstractCalculator::overriddenFilters we need to be able to
tell appart array based on their values and indices
Reduce SQL queries for chart #2340
Reduce SQL count for geoname for chart #2340

By getting children and grandchildren, we avoid subsequent
queries when asking for a region
Aggregated trend lines cannot be linked to detailed tables #2340
Save a few SQL queries for chart panel #2340

This could be optimized much more, but we better wait to
implement #2639
Fix e2e tests for parts side by side