Add: core - update() in mananger
Mod: move ViewmodelInfo out of defs
Mod: core - some manager interfaces become optional
Add: core - frame-dependent tracker, aka single object tracker
Add: wrapper - half of the pixel-track (2013) implementation
Add: core - basic single object tracking (tested)
Mod: move search window to basic class for visualization
Add: wrapper - opencv meanshift tracker (standard, Hue only)