Some small fixes

[bentideswell]

This contains 2 fixes:

1. The first fix wraps the prepareShipment parameter in an array. Magento requires this to be an array so just passing the ID triggers a warning. This breaks functionality if errors aren't hidden.

2. Moved the sales order grid action label to it's own method rather than a hard coded string. This makes it easy for devs to modify this without having to rewrite the whole observer.

[IbrahimS2]

@mikkelson Why the repo is abandoned?

[mikkelson]

@bentideswell Thank you for these fixes, sorry we've not got round merging yet. We still to test this across all support versions, I'll see if we can get this done next week.

@MageSuper It's not abandoned, but it has taken less significance since the release of Magento 2 and especially since the end of support for Magento 1 announcement.