Adding "scope" subcommand

Setup a scope subcommand for setting/viewing/unsetting a cloudlet and
blueprint scope for other commands.  In the process, cleaned some files
and added a bit of error handling.  This is not plumbed in anywhere yet,
however, because it is actually somewhat more complex to do so than I
expected, so scope is disabled for the time being.
Fixing blueprint argument error
Renaming ContextManager and cleanup

Renaming ContextManager -> Context fixes #118.  Also code cleanup,
removing some unnecessary getter/setters, adding a bit more
documentation.
Merge pull request #122 from huit/118-context-manager

Renaming ContextManager and cleanup
Merge branch 'master' into 117-scope-commands

Conflicts:
	bin/nepho
Merge pull request #121 from huit/117-scope-commands

Adding "scope" subcommand
Allow operating in "offline mode" if cloudlet registry cannot be
updated.  Fixes #123.
Merge pull request #124 from huit/123-registry-timeouts

Allow operating in "offline mode" if cloudlet registry cannot be
Cleaned up formating on cli/stack.py
Clean up formating in cli/parameter.py
Cleaned up formating on cli/config.py
Cleaned up formating on cli/cloudlet.py
Cleanedu p formating on cli/base.py