Update copy in various places throughout app

[sammyd]

Finally got the approved copy for various screens in the app

Screen	Details	Changes
No access	If you don't have an active subscription	HL: Sorry, subscribers only
		Body: The raywenderlich.com mobile app is only available for subscribers. To learn more, visit raywenderlich.com/subscription.
		Button: Sign Out
Sign In Screen	May well get different art.	Body: Stay committed to continuous learning and becoming a better mobile developer with access to the entire raywenderlich.com tutorial library on your mobile device!
2nd Page Sign in	If you have pages on the signing screen	Title: Take your videos on the go
		Body: Did you know that Professional Subscribers can download & watch videos offline on our app? They also get exclusive access to advanced courses!
Downloads, when no access	i.e. doesn't have permissions for downloads	Copy: Professional subscriber benefits include being able to download videos and watch them offline, access to exclusive content, and more!
	Should link to https://store.raywenderlich.com/products/subscription	Button: Manage subscription
Pro Course Locked	The blurred image at the top, with the padlock	Add a Button that links to the same place as the previous row. Text: Manage Subscription
		Copy: To unlock this course, become a Professional subscriber. Professional subscriber benefits include being able to download videos and watch them offline, access to exclusive content like this, and more!

There may well be some updating of artwork on these and other screens too, but I will let you know.

Gimme a shout if any of this doesn't make sense. Ta!

[luke-freeman]

@rachitmishra This is all done