Add fabfile generation to pelican-quickstart

This commit adds optional fabfile.py generation during the
pelican-quickstart process. Reasons include:

* "make" is cumbersome to install on Windows
* Fabric runs in any Python environment
* fabfile is just Python and thus more flexible and extensible

This is an initial implementation and does not currently provide as many
upload options as its Makefile counterpart.

Refs #584.
Fix file endings for examples

reStructured should use reStructured for linked documents. Markdown should use Markdown for linked documents.
Merge pull request #986 from TheHippo/patch-1

Fix file endings for examples
Add documentation for WITH_FUTURE_DATES

Closes #952
added THEME_STATIC_DIR setting

The theme static output directory path is now customisable via settings.
i.e. you can now use 'assets' instead of 'theme'.
Start a section about plugin recipes in the docs
Merge pull request #989 from getpelican/plugins-recipes

Start a section about plugin recipes in the docs
Merge pull request #970 from russkel/themestaticdir

added THEME_STATIC_DIR setting
Correct URL for pip install editable in docs

Refs # 975