spray 1.0-16

• add a sticker
• consistently use coeffs(); return a disord object
• constant() now generic
• cross products implemented as spraycross()

spray 1.0-17

• sprayvars option now also governs atrix-form printing
• drop() function added, following the clifford package

spray 1.0-18

• bug in coeffs(x) <- v fixed
• == implemented, also !=
• new generic as.id()

spray 1.0-19

• bugfix so getOption("max.print") is respected
• coeffs(S) returns drop()-ped values