Various improvements

• renamed norm and accumarray functions
• removed convmtx function (can be realized with conv2 and eye)
• or, and functions are now Y|, Y&
• new "increment by 1" and "decrement by 1" functions (Q, q)
• next-prime and totient functions have been moved
• break and continue are now unconditional
• clipboard M has been extended to 4 function calls, and inputs can be addressed individually.