New built-in functions and array operations

• palette(z) returns the current RGB palette color mapping z into cbrange.
• rgbcolor("name") returns the 32bit ARGB value for a named color.
• index( Array, element ) returns the first index i for which Array[i] is equal to element. See arrays.
• User-defined functions allow an array as a parameter.
  Example: dot(A,B) = sum [i=1:|A|] A[i]*B[i]
• Array slices are generated by appending a range to the array name. Array[n] is single element. Array[n:n+5] is a six element slice of the original array. See arrays, slice.
• split("string", "separator") unpacks the fields in a string into an array of strings. See split.
• join(array, "separator") is the complement to split. It concatenates the elements of a string array into a single string with field separators. See join.
• stats <non-existent file> yields a testable value. See stats test.
• stats $vgrid finds min/max/mean/stddev of voxels in grid