split out a build command from the synapsectl deploy command

[emmazhou]

this PR looks huge but is mostly copying code directly out of deploy.py into build.py.

the following should now work:

synapsectl build /path/to/app
synapsectl build /path/to/app --skip-build  # this will skip compiling in docker and just package a deb

the deploy command remains unchanged if you call it the same way:

synapsectl -u <scifi_name> deploy /path/to/app  # builds, packages, and deploys as before

but you can also now bypass building and packaging by passing a package instead of a path:

synapsectl -u <scifi_name> deploy --package /path/to/your/deb

[maxhodak]

works for me