Initial hosted API documentation

[pdavidc]

Establish hosted API documentation on the gh-pages branch. Push an initial static site containing API docs from the develop branch.

[pdavidc]

Initial documentation is live via this project's GitHub pages branch:
https://nasaworldwind.github.io/WorldWindAndroid/

git checkout develop
./gradlew build
cp -R worldwind/build/outputs/doc/javadoc ~
git checkout --orphan gh-pages
git rm -rf .
rm -rf * .idea .gradle .DS_Store
cp -R ~/javadoc/ .
git add -A
git commit -a -m "Initial hosted API documentation"
git push origin +gh-pages