Now after changing Context.h 488 modules will be recompiled instead of 582.

With tons of MATERIALIZED VIEW attached to one table pushing to this
views can be pretty memory consuming due to blocks squashing, add
ability to control this separatelly for MATERIALIZED VIEWs.

Plus squashing is useless if the underlying engine is Buffer().

 * "lock_acquire_timeout" controls for how long a query will continue to
acquire each lock on its argument tables
 * "lock_acquire_timeout_for_background_operations" is a per-table
setting for storages of *MergeTree family

* Move some code outside dbms/src folder
* Fix paths