Fixed Lua code block formatting in box_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

Regression introduced by 9036eeeb

* wallarm button alignment
* better action calls
* remove obsolete benchmarks & example

Conflicts:
	doc/sphinx/dev_guide/building_documentation.rst

Failed in a plane.