environment viewer first checkin - no worky
Merge branch 'develop' into feature/enviewer
partial progress on environment viewer

some types display properly
not automatically triggered yet (instrumentation of cell.eval fails)
Merge branch 'develop' into feature/enviewer
bad pun
build.sh do not build all packages by default

for @s-u
replace --skip-headers with --all to reverse the default behavior
pull build_package out of build.sh into its own script

to build a single package, do e.g.
scripts/build_package.sh rcloud.packages/rcloud.enviewer
basic environment and dataframe support

still no automatic update of environment
automatically refresh environment viewer on cell execute

by adding execution_watchers to notebook_model
Merge branch 'feature/enviewer' into develop