Modify build_ogc_app.py to break process into independent steps that can be run independently

[mcduffie]

Modify build_ogs_app.py to have a command line interface similar to Git or Docker where subcommands are run from a directory and can be independently called. This would better fit with the CI/CD process and make the program usable manually without requiring all steps be run.

[mcduffie]

Implemented at 1b97492

[mcduffie]

Example usage:

tmp_dir=/tmp/app_gen_test

rm -rf $tmp_dir

build_ogc_app.py init \
    git@github.com:unity-sds/unity-example-application.git $tmp_dir

cd $tmp_dir
build_ogc_app.py build_docker
build_ogc_app.py push_docker quay-development-alb-656354332.us-west-2.elb.amazonaws.com:8000/mcduffie
build_ogc_app.py build_cwl