Update Documentation for 5.0.0

[aaronayres35]

targeting [gh-pages]

These are the steps I followed for building the documentation:

git clean -ffxd
git checkout 5.0.0
python etstool.py install
git clean -ffxd
python etstool.py docs
git checkout gh-pages
git pull
git checkout -b gh-pages-5.0
mkdir 4.5
mkdir 5.0
rsync -r --exclude="\.buildinfo" docs/build/* 5.0/
rm -r docs
mv `ls -d [![:digit:]]*` 4.5/
git add -u
# manually delete the `4.5/apptools` subdirectory filled with `__pycache__` (somehow snuck passed my git cleaning)
git add 4.5/
git commit -m "move current documentation into 4.5"
cp -r 5.0/* .
git add .
git commit -m "create new 5.0 folder and add current docs there and to root directory"

To test:
python -m http.server

Checklist
- [ ] Add a news fragment if this PR is news-worthy for end users. (see docs/releases/README.rst)

[rahulporuri]

I checked out this branch locally and served the docs - LGTM.