Prepare for splitting up Getting Started docs
Split Getting Started docs into separate sections

The "Getting Started" docs became overly long and unwieldy over time.
This splits it into separate sections, including:

* Quickstart
* Installation
* Writing content
* Publish your site
If PATH is undefined, Pelican uses PWD as content
Merge pull request #1345 from justinmayer/docs34

Split "Getting Started" docs into separate sections
Fix RstReader authors metadata processing

The reader would return a list of authors already, but
METADATA_PROCESSORS['authors'] expects a string.
Added a test case for this (only the HTMLReader had it).
Docs update for *_{previous|next}_page variables
Merge pull request #1362 from avaris/neighbor_pages_docs

Doc update for *_{previous|next}_page variables
catch arbitrary exceptions during cache unpickling

It is hard to forsee what could be raised.