Add `update` CLI

[azukaar]

Add a functionnality to update installed packages.

Options

# Check updates
g update

# Actually perform the updates
g update --perform

# Only for patch | minor | major
g update --patch | --major | --minor 

# Actually perform the updates on the minor only, for the package React
g update --minor --perform npm://react

Behaviour

• Add a "packageUpdate" hook to update a package
• Add a "checkUpdate" hook to perform update check
• Check on updates available by crawling the top level dependencies in gupm.json and checking if any package in the same repository are available to update
• Check another file than gupm.json if provider has something else setup
• Perform update with --perform following the same rules than the checks