reorg of docker container to remove layers

[lwasser]

Still building but throwing an error when rasterio is imported but it still imports into notebook.

• finally figured out why tags are not generated. we have custom hooks. running a test to add a tag.
  This pr does

1. a reorg of the dockerfile to keep things smaller
2. adds a hook that

• when a build happens on the master branch, the tag: latest is updated. this is important because most people just do a docker pull and docker pull defaults to latest. Latest is however manages in that it is only updated when a push happens from master branch. it also creates the SHA as a tagged build
• when not on master, it will build a tagged version that is the name of the branch. this makes it easier to identify hashs that have been fully approved vs those being tested.

i've tested this locally and it works but now let's see what happens when this is merged.