update reference manual: add specification querying API

[GoogleCodeExporter]

The specification querying API introduced by fixing issue #17 and issue #19 still
has to be documented in the online documentation.

Original issue reported on code.google.com by Christoff.Buerger on 18 Jun 2013 at 12:22

[GoogleCodeExporter]

To document the specification querying API (RACR reflection) is postponed until
the RACR meta-language is stable.

Explanation of RACR meta-language: RACR is currently implemented in itself.
This means, that a RACR language is given to specify the RACR specification
language. In consequence, specifications are just ASTs of this meta-language,
such that AST rules, productions, symbols, attributes and respective analyses
on specifications are AST nodes and attributes of the RACR meta-language. The
meta-language can be queried using RACR's query API (ast-child, att-value
etc.), such that no special specification querying API is necessary.
Nevertheless, the meta-language still has to be documented.

Original comment by Christoff.Buerger on 13 Mar 2015 at 1:53