Move Deep Link Resources into their own namespace

Summary of Changes

This moves anything named LtiDeepLinkResource* into it's own DeepLinkResources namespace. It also abstracts a HasDimenions trait for shared usage.

Man, I really tried to make it understand that I was moving files. I even did git mv. Still, it didn't quite get it. Sorry.

[x] Depends on https://github.com/packbackbooks/lti-1-3-php-library/pull/121

Testing

[x] I have added automated tests for my changes
[x] I ran composer test before opening this PR
[x] I ran composer lint-fix before opening this PR

packbackbooks / lti-1-3-php-library

Move Deep Link Resources into their own namespace #124

Summary of Changes

Testing