Update global-actions.R documentation and filename

[apulsipher]

• Change filename of global-actions.R to global-events.R to match internals
• Update documentation on add_globalevent to clearly distinguish between current and deprecated usage
• Update rm_globalevent to take a name as the second parameter to match the underlying function call of rm_globalevent_cpp and to make the usage clearer
• Update rm_globalevent documentation to match above changes. At the moment the documentation for add_globalevent and rm_globalevent are shared, but the usage is different enough that these should be separated