Documented all lua binds directly in the source

This change adds a comment to each lua binding. In the future a script should
parse those and generate the docs from them.

This should prevent outdated docs and duplicate effort to keep code and docs
synced.

In C++ categories can be defined in this way:
~~~ c++
/** LUA_CATEGORY long description of the category (shortname)
 * further text
 * goes into
 * the next lines
 */
~~~

The shortname is only used to bind other comments to the category.

In lua the category would look like this:
~~~ lua
--- LUA_CATEGORY long description of the category (shortname)
-- further text
-- goes into
-- the next lines
~~~

A comment that describes a bind then can look like this:
~~~ c++
/** LUA some_function (shortnameofcategory)
 * some_function(string name)
 * some_function(int id)
 **
 * Description
 */
~~~

Or in Lua:
~~~ lua
--- LUA some_function (shortnameofcategory)
-- some_function(string name)
-- some_function(int id)
---
-- Description
~~~

Autoupdates script follows soon