turned on strict references
added Symbol.isHybrid
added Card.isHybrid
got all the frame stuff rendering correctly through the Velocity template
split CoreGroup into ArtGroup, RulesGroup, and RulesOptionalGroup to force spells to have rules (i.e., what the spell does), but leave other card types with supported-but-optional rules
converted the old test cardset to the new structures in the theme module
added a couple derivation methods to SimpleTexture for creating new ones based on existing ones
filled out the rest of the ColorTheme map, though everything is just the metal texture with a tinted flood with colors I completely guessed on
for color-allied lands, use the normal textbox texture as a fall back if there is no mana textbox texture
generate all the cards in the test set along with a proof sheet.
added a ignore for root-level svg files (which is where proofs end up)
 * renamed 'invert' to 'negate', and told it to not negate zero
 * loop over the textbox textures when setting up references, not the frames, because there can be different numbers