Add some NULL-checks to WidgetScrollBox

Fixes #1037
Cache dragged MenuManager icons in a Sprite

Closes #978
Add round() replacement for MSVC
Merge pull request #1038 from dorkster/fixes

Fix #978 and #1037
Merge branch 'master' of https://github.com/igorko/flare-engine into testing
Grab "full" filename for EnemyGroup enemies
Use full path for spawn/transform actions
Merge pull request #9 from dorkster/enemy_type

Fix up remaining enemy type bugs