Merge Changes from `master` to `dev`. (#722)

* - Update tensorflow version to 1.15.0
- Add doc for Jetpack 4.4
- Remove opencv installation

* Add dataset and pre-trained model page

* fix issue #634 (#646)

- remove jquery dependency
- add clearTimeout

* Allow overriding WEB_CONTROL_PORT from env variable

* pin h5py version

* fix h5py version for mac

* * Update doc with donkey train command. (#709)

* Update doc with developer section for building own models in donkey 4.1
* Integrate changes from PR feedback

Co-authored-by: Jonathan Tse <jonathan@tsez.net>
Co-authored-by: Tawn Kramer <tawnkramer@gmail.com>
Co-authored-by: DocGarbanzo <47540921+DocGarbanzo@users.noreply.github.com>