Reorganize and expand quickstart big picture docs on environments

* Add Environments section under "Understanding the Fundamentals" to introduce environments. This uses the glossary definition as a starting point and expands on it a little.
* Move the Web Profiler discussion out of Working with Environments into a separate section, and add a paragraph briefly summarizing what the profiler can do.
* Improve the Working with Environments section.
* Original changes from PR #2683 rebased on 2.2
Big Picture Environments cleanups

* Move the environments and front controller discussions to book/page_creation
* This allows for the debug toolbar discussion to be more prominent
Removing duplicate content

The same content can be found at the end of the "Configuration and setup" section. I've removed the more recent content, and because I think the right place is in the "configuration" section.
Changes for correctness
some typos
Update propel.rst
Merge pull request #2823 from jbafford/big-picture-environments-22

Improve Quick Tour "Big Picture" section and expand Environments docs
Fixing some syntax errors I caused
Fixing typo
[#2823] Complete re-reading of the big picture quick tour document

* Making things shorter where possible
* Being more consistent in web server setup and URLs
* Improving language, wording, etc
fixed inconsistency in code examples.
fix brace on the next line to be on the same line
Merge pull request #2828 from gregquat/patch-19

Removing duplicate content
Merge branch '2.2' into 2.3

Conflicts:
	book/templating.rst
	quick_tour/the_big_picture.rst