The top index now points to three files: setuptools.txt (user guide),
development.txt (development guide) and a WIP index file that is to
summarized deprecated practice that remains relevant for backward
compatibility.

doc overhaul step 1: simplify index and group deprecated files

Did a cut and paste from setuptoo.txt to userguide/quickstart.txt

Did a cut and paste from setuptools.txt

cut-and-paste from setuptools.txt

cut and paste from setuptools.txt

from pointing at setuptools.txt to userguide/index.txt

doc overhaul step 2: break main doc into multiple sections

from quickstart.txt to functionalities.txt

so that the quickstart is cleaner for now. Might add more text later

egg-secutable section moved from userguide/functionalities to deprecated/functionalities

such that each section is comprised of a quick intro and example
that illustrate the use of that functionality and provide a link
to a more detailed explanation.

outline is completed, now to fill the donut holes

those that don't need to put into a dedicated file
are now inside the miscellaneous.txt

Step 4: A PEP517-styled quickstart user guide and room for collaboration

userguide/pkg_discovery.txt now covers find_package,
find_namespace package and legacy use of namespace
package creation in both setup.py and setup.cfg style

Step 5 on 2093: Package discovery and namespace package userguide now ready

The `decalrative config`_ link present higher in the document is also
unresolved, I'm not quite sure what the intended target was.

Coverage
1. console_script
2. plugin support
3. optional dependencies

…tch to imperative voice. Limit to declarative config (setup.cfg) examples.

Step 6 on 2093: userguide on entry points now available

…type

note the use case for tests and docs functions and that "test_require" is deprecated, shorten description of the example

step 7 on 2093: dependency management guide ready