This patch explicitly saves Exception to a thread-local variable inside
struct cord on tnt_raise(). This variable can be used to safetly
re-throw last exception from any place (not only from catch() block).
This technique requires exception to be thrown and catched by pointers.
tnt_raise macros was rewritten and all 'catch (Exception &)' blocks were
substituted with 'catch (Exception *e)'.

This patch also adds a new feature to box.raise() function.
When called without arguments box.raise() re-throws last exception (if
any).

These changes needed to implement proper handlings of exception for FFI
calls.

- Drop GE/LE iterators for HASH-index.
- min/max can receive key.
- fix all tests.

+ use luaL_ref/luaL_unref to store lua scalar instead lua metatable.
+ add :is_closed method.

Update the protoco spec in doc/box-protocol.txt.
Update box.net.box with a bunch of hacks.
Update the python driver.

Remove support for flags variable (BOX_RETURN_TUPLE).
It was not tested anywhere! (-> kill)

Implemeng Lua msgpack.next() to support streamed processing.
Add tests.

Fix a bug with messed up aliases of msgpack.dumps() pointing
to encode() and loads() pointing to decode() (should be vice versa).

    1. Unified blurb for every site page
    2. remove tnt-html.xsl.cmake tnt-html-chunk.xsl.cmake in favor of
    --stringparam and -param flags of xsltproc and saxon
    3. Create flags for input/output in static.py script for OOS build

All layouts are in doc/www-data.in/_layout and are written in Jinja1
(django-like templates). All texts are in doc/www-data.in/_texts

Text files contains YAML files with chunks of markdown strings:
```
$module:
    $uno: |
        some text in markdown
    $dos: |
        it may be multiline
    $tres: |
        # header 1
        ```
        may have some embedded code
        ```
        e.t.c
    ...
```
where `$module` is name of layout file, `$uno`, `$dos`, `$tres`... are
name of parts (template parts `{{ $module.$part }}`)
Site still stores files in `doc/www-data` for copying on server.
Also it integrates documentation (only on stable/master branches) into site (still templlates)
Usage of new `extra/static.py`:
```bash
$ cmake . -DENABLE-DOC=TRUE
$ make
$ cd /doc/www-data.in/
$ ../../extra/static.py site `# build site`
$ ../../extra/static.py docs `# embed docs`
```

 ### documentation building

Add `html-saxon-chunk` and `html-chunk` targets for building chunked
html documentation.

`make` in `doc/user` now builds `html-saxon` and `html-saxon-chunk`
targets

> remove script/ directory and move it's content to extra/