Move screen-edge alignment to util function
Add configuration file for title screen layout
Don't handle icons in SDL2Renderer
Suppress error message when engine/mouse_cursor.txt can't be opened

Modded mouse cursors is an optional feature, so we don't need to display
a message if we don't have it.
Merge pull request #990 from dorkster/fixes

Suppress error message when engine/mouse_cursor.txt can't be opened
Move title screen music to engine/default_music.txt
Merge pull request #992 from dorkster/title_screen

Move title screen configuration to text files
Merge remote-tracking branch 'upstream/master'
Remove x_origin and y_origin from WidgetLabel

Fixes #991
Merge pull request #993 from dorkster/label

Remove x_origin and y_origin from WidgetLabel
Merge remote-tracking branch 'upstream/master'