* draw lattice boundingboxes in 3dView [if "show_bounds" is used -- an option previously pretty useless for lattices]
* give proper values for lattice objects ".bound_box" in bpy
* give proper values for armature objects ".bound_box" in bpy
* lets users use "Dimensions" [in 3dView Transform panel] on lattices and armatures
* remove redundant calculations in "boundbox_armature()"
Armatures boundingboxes were already drawn in 3dView, if "show_bounds" was used.
Based on report T45735: Lattice's bounding_box doesn't update,
and a comment in code by @campbellbarton ("later we may want to add dimensions for lattice, armature etc too").
Revision: https://developer.blender.org/D1460
3fa0a1a5bc