* se_of()
* phia_document_setobject()

The generic, type-unsafe API is used for stream merges only.
Don't use it in places in which it obscures the code.

Macros make it difficult to navigate around the code, tags or not.

Remove another few lines of unused code.

Remove .drop, .getobject, .setobject, .cursor from soif

Remove an unused global view at the database.

Set a memory limit in Phia. Fix the quota accounting.

* remove document expire
* remove snapshotting, anticache, memory-only modes
* remove unused box.cfg.phia settings

Remove "optimized" autocommit code when working with a single index,
tarantool always creates a transaction in engine even for
autocommit mode. This optimization, in other words, could
(potentially) save only a little bit of CPU in case of
autocommit and only-primary-key space.

* remove trigger (not used)

* remove the built-in write ahead log (never used in Tarantool)

We need an online backup for all engines. The current
backup in phia only works when its own write ahead log is enabled,
which is never the case with tarantool.
@todo: add rsync-friendly backup to phia, just like
is already the case for memtx.