Version check

[eseiler]

We should check that the documented behavior reflects the actual behavior. For example,

sharg-parser/include/sharg/detail/version_check.hpp

Lines 339 to 356 in 0f91e17

	#######################################################################
	Automatic Update Notifications
	#######################################################################
	This app can look for updates automatically in the background,
	do you want to do that?
	[a] Always perform version checks for this app (the default).
	[n] Never perform version checks for this app.
	[y] Yes, perform a version check now, and ask again tomorrow.
	[s] Skip the version check now, but ask again tomorrow.
	Please enter one of [a, n, y, s] and press [RETURN].
	For more information, see:
	https://docs.seqan.de/sharg/main_user/about_update_notifications.html
	#######################################################################

Says that the default is yes, but it is actually (and should be) never.

Personally, I often have to double check what version_check::on does. It doesn't mean always, but rather that it should ask the user. So maybe version_check::ask would be a better name.