1.0_beta23: Sapporo

Fixes:
 - Saving an m3l file sometimes damaging the first few bytes of a rom,
 making it unreadable
 - restored auto save level length not being set correctly
 - rendering of vertical vine and pole when next to another block
 (thanks @PiJoKra)

Added:
 - Scroll to and select objects/enemies, when hovering over a warning
 - Dark theme (thanks @fortenbt)
 - Option to show object/enemy name and position tooltip on mouse over