Usage of the skeleton generator for Alqua documents

01. Create a correct YAML metadata file for your document based on the
'new_metadata.yml' file in the root of this repository. This file doesn't need
to be in the same folder as the document source files (e.g. LaTeX).

02. cd to the 'Templates' folder. This is needed to put it directly in the
Python import path so the 'import' statements in each Python module can work.

XXX: we could avoid the step above packaging the Alqua editing pipeline into a
Python egg.

03. Execute the rendering script typing 'python render.py
<path-to-metadata-file>', where <path-to-metadata-file> is the full (relative
or absolute) path to the file created in step #01. 
This will generate a folder with the name of the id of the document referred,
contaning a set of skeleton files, which are just the Alqua templates filled
with the metadata from the document YAML file.

04. Copy all these files to the root folder of your document. Copy also the
whole folder named 'aq-aux', which you can found right inside the 'Templates'
The file named '<id>.tex' (for LaTeX-based documents) is the main file you have
to compile. All other files starting with 'aq-' are auxiliary files included
from the main one.

06. Check that you have the files '<id>-preamble.sty' and '<id>-settings.sty'
in the root folder of your document, even if they're empty.

05. Try to compile the main '<id>.tex' file and check the error output. Correct
errors and try again until it compiles successfully. Keep in mind that you
might have to run associated programs like bibtex, or even to modify the
metadata and generate new skeleton files, that is, to come back to step #01.

You may want to commit each step you take to make it compile correctly as a
separate Mercurial changeset.