Primary graphic now sent on reconnects

[NicoleYarroch]

Fixes #961

This PR is ready for review.

Risk

This PR makes no API changes.

Testing Plan

• Added missing initializer and stop test cases for each of the Screen Manager's sub managers.

Summary

Displaying a primary graphic in a SDLShow on reconnects failed when the image was a duplicate of the one being displaying on disconnect. This is because the manager thought the image was already being displayed. The SDLTextAndGraphicManager's currentScreenData is now reset on disconnects.

Changelog

Bug Fixes

• Fixed displaying a primary graphic in a SDLShow on reconnects failing when the image was a duplicate of the one being displaying on disconnect.

CLA

• I have signed the CLA

[joeljfischer]

SDLTextAndGraphicManagerSpec should be updated for the following cases:

• it(@"should instantiate correctly") should include _currentScreenData.
• Check that stop resets everything correctly.

[NicoleYarroch]

SDLTextAndGraphicManagerSpec should be updated for the following cases:
it(@"should instantiate correctly") should include _currentScreenData.
Check that stop resets everything correctly.

Fixed. I also added test cases to the other screen manager submanagers.