fixed #693 : adding - to valid username in Rserve
Merge branch 'develop' into add-dash-to-username
environment viewer first checkin - no worky
This Fixes #952

The string replacement I have done using regex is a crude way. Need to get a better way to handle this.
@gordonwoodhull you can review this and let me know if you feel there is another better way.
Merge branch 'develop' into feature/enviewer
don't fail if an image doesn't have the alt tag
partial progress on environment viewer

some types display properly
not automatically triggered yet (instrumentation of cell.eval fails)
suppress warnings and messages for add-on packages

fixes #934, very crudely

@s-u, is there a better way to do this - should we divert these messages to a
log or something?  In particular, we don't want to hear about the packages being
loaded, and we don't want to hear that `View` has been masked.

But I suppose if people are developing their own RCloud add-ons, they'll want to
know if something goes wrong, and this will keep them in the dark.
Merge branch 'develop' of https://github.com/att/rcloud into develop
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
fix bug in environment sorting
fix session disconnect for environment viewer in a very stupid way

we must need some kind of session shutdown event?
rcloud.notebook.cells extracted from rcloud.call.notebook

new ocap returns notebook cells in sorted order
rcloud.call.notebook still needs to be modified to use this
rcloud.enviewer do not try to install UI stuff if not in UI

why you would ever load this library without a UI i don't know
but currently we load add-ons for all sessions not just UI
fix false start at refactoring