Use the same metavar name for packages in create and install
Fix typo
Use the same metavariable for conda update as conda install
Merge conda install, create, and update cli code

I haven't yet merged the command line flags code.
Factor out command line options for install, update, and test

This makes things as uniform as possible, and adds some new features to update
and create that were previously only available to install.

One backwards incompatible change is that conda create -f now means --force
instead of --file.
Update changelog
Merge branch 'master' into install_create_merge

Conflicts:
	CHANGELOG.txt
Cleanup
Merge pull request #510 from conda/install_create_merge

This is work on merging common code from update, install, and create