Get rid of one-letter `i` variables.

- Move phia_tuple_from_data() and phia_tuple_from_key() to phia.c
- Make tuple_upsert_execute() to be C-friendly
- Move phia_upsert_cb() and related stuff to phia.c

Prepare to switch to MessagePack.

- Fix code style
- Remove useless tnt_raise() from tuple_compare_field()
- Use mp_decode_strbinl() for bin/str comparison

`struct si` has longer lifecycle than `PhiaIndex`.

- Replace sfscheme->field_count with sfscheme->keys_count + 1.
- Keep only key parts in sfscheme->fields, remove value

- Remove position_ref, position_key, key from sffield
- Remove keys from sfscheme
- Remove sf_schemeadd and sc_schemevalidate
- Use uint32_t instead of int

Prepare to switch to Msgpack.
MsgPack is variable-length encoding, even for uint64 number.

* remove ss_bufinit_reserve(), it gave nothing in performance
  but obscured memory leak search

- Move to --long
- Simplify check_test()
- Remove unused code

* remove unused code in transaction manager

* split transaction commit to prepare and commit, commit
  it after write to the write ahead log

* simplify quota init
* simplify env init
* simplify transaction init

Get rid of assert(0) and assert(false).

Conflicts:
	doc/sphinx/book/administration.rst
	doc/sphinx/book/app/e-phia/i1.png
	doc/sphinx/book/app/e-phia/i10.png
	doc/sphinx/book/app/e-phia/i12.png
	doc/sphinx/book/app/e-phia/i13.png
	doc/sphinx/book/app/e-phia/i14.png
	doc/sphinx/book/app/e-phia/i2.png
	doc/sphinx/book/app/e-phia/i3.png
	doc/sphinx/book/app/e-phia/i4.png
	doc/sphinx/book/app/e-phia/i5.png
	doc/sphinx/book/app/e-phia/i6.png
	doc/sphinx/book/app/e-phia/i7.png
	doc/sphinx/book/app/e-phia/i8.png
	doc/sphinx/book/app/e-phia/i9.png
	doc/sphinx/book/app/e-phia/index.rst
	doc/sphinx/book/app/e-sophia/i1.png
	doc/sphinx/book/app/e-sophia/i10.png
	doc/sphinx/book/app/e-sophia/i12.png
	doc/sphinx/book/app/e-sophia/i13.png
	doc/sphinx/book/app/e-sophia/i14.png
	doc/sphinx/book/app/e-sophia/i2.png
	doc/sphinx/book/app/e-sophia/i3.png
	doc/sphinx/book/app/e-sophia/i4.png
	doc/sphinx/book/app/e-sophia/i5.png
	doc/sphinx/book/app/e-sophia/i6.png
	doc/sphinx/book/app/e-sophia/i7.png
	doc/sphinx/book/app/e-sophia/i8.png
	doc/sphinx/book/app/e-sophia/i9.png
	doc/sphinx/book/app/e-sophia/index.rst
	doc/sphinx/book/app/e_sophia/i1.png
	doc/sphinx/book/app/e_sophia/i10.png
	doc/sphinx/book/app/e_sophia/i12.png
	doc/sphinx/book/app/e_sophia/i13.png
	doc/sphinx/book/app/e_sophia/i14.png
	doc/sphinx/book/app/e_sophia/i2.png
	doc/sphinx/book/app/e_sophia/i3.png
	doc/sphinx/book/app/e_sophia/i4.png
	doc/sphinx/book/app/e_sophia/i5.png
	doc/sphinx/book/app/e_sophia/i6.png
	doc/sphinx/book/app/e_sophia/i7.png
	doc/sphinx/book/app/e_sophia/i8.png
	doc/sphinx/book/app/e_sophia/i9.png
	doc/sphinx/book/app/e_sophia/index.rst
	doc/sphinx/book/index.rst

Review fixes:
* revert changes in console.lua, they should be pushed down to
  net.box (it should accept empty passwords)

Previously the URI BNF didn't allow to specify empty
password. There should have been at least one symbol.

Now both user@host and user:@host forms are permitted.

In case of user@host, the password will parsed as nil.
In case of user:@host, the password will be parsed as
empty string.

Fixes #1512