Fixed escaping in files generated from quickstart

Variables are properly escaped before they are replaced in the
templates.
Correctly use the right variable for webassets

According to [the webasset docs](http://webassets.readthedocs.org/en/latest/integration/jinja2.html#using-the-tag)
the variable should be `ASSET_URL` instead of `ASSETS_URL`.
Apply the string formatting to {TAG,CATEGORY}_FEED urls.
Add sleep to no files exception to avoid CPU load
Monospace default values of settings
Fix the settings about DATE_FORMAT*S*. Fix 540
Don't force the number of categories to be equal to 1. Fixes #521
Change the background color of the code-blocks on the default theme. Fix #511
merge upstream
fix the tests
merge rachid changes
oops
add gittip to the output
Add a new signal article_generator_finalized, called at the end of ArticleGenerator.generate_context
Add a multi_part plugin

It list all parts of a blog post, helping to create a navigation menu between all the parts
remove useless default_settings param in configure_settings
refactoring so that command line options override settings

and Pelican class now accepts a single parameter ``settings``
So that Authors display and output can be disabled for single user sites, allow the AUTHOR setting to be set to an empty string ''.
An author is needed, but was defaults to OS user, or 'John Doe'. If a blank author is provided, it generated authors/.html file, and templates display just "by "
Updated generators.py and templates to ignore Authors objects which have a blank name
Amended utils copy so that a warning is produced if a source file is not found in FILES_TO_COPY whilst copying. eg if there is a typo in the file name, or the file is moved.
Merge pull request #543 from Lothiraldan/master

Add a new signal article_generator_finalized, called at the end of ArticleGenerator.generate_context