Add support for triples of positions in volume (#321)

* Add support for triples of positions in volume

it work good!

* Updating docs

* made it work with 5 arguments

so like volume(x,y,z,pos) or volume(pos,x,y,z).
Also renamed previous variables

* updated docs

* making it smarter

* made it work for rect and diamond

and cleaned up some earlier code

* updated docs

* did all ur stuffs

* fixin the issues

docs/scarpet/Full.md

@@ -2346,10 +2346,11 @@ which would cause the expression not be evaluated for their boolean value.
 `scan` also handles `continue` and `break` statements, using `continue`'s return value to use in place of expression
 return value. `break` return value has no effect.
 
-### `volume(x1, y1, z1, x2, y2, z2, expr)`
+### `volume(x1, y1, z1, x2, y2, z2, expr), volume(pos1, pos2, expr)`
 
 Evaluates expression for each block in the area, the same as the `scan` function, but using two opposite corners of 
 the rectangular cuboid. Any corners can be specified, its like you would do with `/fill` command.
+You can use a position or three coordinates to specify, it doesn't matter.
 
 For return value and handling `break` and `continue` statements, see `scan` function above.
 
@@ -2361,15 +2362,19 @@ Returns the list of 6 neighbouring blocks to the argument. Commonly used with ot
 for(neighbours(x,y,z),air(_)) => 4 // number of air blocks around a block
 </pre>
 
-### `rect(cx, cy, cz, dx?, dy?, dz?, px?, py?, pz?)`
+### `rect(cx, cy, cz, dx?, dy?, dz?, px?, py?, pz?), rect(centre, difference?, positive_diff?)`
 
-returns an iterator, just like `range` function that iterates over rectangular cubarea of blocks. If only center 
-point is specified, it iterates over 27 blocks. If `d` arguments are specified, expands selection by the  respective 
-number of blocks in each direction. If `p` arguments are specified, it uses `d` for negative offset, and `p` for positive.
+Returns an iterator, just like `range` function that iterates over a rectangular area of blocks. If only center
+point is specified, it iterates over 27 blocks. If `d` (`difference`) arguments are specified, expands selection by the  respective 
+number of blocks in each direction. If `p` (`positive_diff`) arguments are specified, it uses `d` (`difference`) for negative offset, and `p` for positive.
 
-### `diamond(cx, cy, cz, radius?, height?)`
+`centre` can be defined either as three coordinates, a list of three coords, or a block value.
+`difference` and `positive_diff` can have the same representations, just if its a block, it computes the distance to the center
+as range instead of taking the values as is.`
 
-Iterates over a diamond like area of blocks. With no radius and height, its 7 blocks centered around the middle 
+### `diamond(cx, cy, cz, radius?, height?), diamond(centre, radius?, height?)`
+
+Iterates over a diamond like area of blocks. With no radius and height, its 7 blocks centered around the middle `centre = l(cx, cy, cz)` 
 (block + neighbours). With a radius specified, it expands shape on x and z coords, and with a custom height, on y. 
 Any of these can be zero as well. radius of 0 makes a stick, height of 0 makes a diamond shape pad.
 # Entity API