Summary:
I started with cleaning flags up (removing unused ones, documenting undocumented ones). There were some flags to remove in `QueryEngine`. Seeing how we never use hardcoded queries (AFAIK last Mislav's testing also indicated they aren't faster then interpretation), when removing those unused flags the `QueryEngine` becomes obsolete. That means that a bunch of other stuff becomes obsolete, along with the hardcoded queries. So I removed it all (this has been discussed and approved on the daily).
Some flags that were previously undocumented in `docs/user_technical/installation` are now documented. The following flags are NOT documented and in my opinion should not be displayed when starting `./memgraph --help` (@mferencevic):
```
query_vertex_count_to_expand_existsing (from rule_based_planner.cpp)
query_max_plans (rule_based_planner.cpp)
```
If you think that another organization is needed w.r.t. flag visibility, comment.
@teon.banek: I had to remove some stuff from CMakeLists to make it buildable. Please review what I removed and clean up if necessary if/when this lands. If the needed changes are minor, you can also comment.
Reviewers: buda, mislav.bradac, teon.banek, mferencevic
Reviewed By: buda, mislav.bradac
Subscribers: pullbot, mferencevic, teon.banek
Differential Revision: https://phabricator.memgraph.io/D825
