autoarchive at startup is a option now, add manual archiving via menu, add global options

- add a global option pane with some explanation and the option for the archive time: manual or at startup
- add menu entry
- add option implementation:
	- do archiving at startup only when option is set
	- add possibility to do manual archiving
	- don't archive if another archiving is running
add a simple toolbar button
add default value for preference
mention toolbar in global options
add confirmation dialog before starting manual autoarchive

to inform user about a needed internet connection
raise version to 0.9.1
improve english confirmation message (for manual autoarchive)
correct some spell errors