Support for partial update of parameters in :drag and :inverse

[baku89]

By reference to @nariakiiwatani's tweet
https://twitter.com/nariakiiwatani/status/1281937067040112640

[baku89]

Introduced the new syntax for the return value of handle drag function. 8f6b94e

Though previously drag function always returns vector, now it should return a hash map having specific keys.

;; Suppose original function call is (+ 0 1 2).
;; Below lines show a form of the returned value of drag function
;; and how it updates a parameter

;; Update all parameters
{:params [x y z]} ;; -> (+ x y z)
[x y z] ;; shorthand

;; Partial update by enumerating tuples of [index, new-param]
{:replace [[0 x] [1 y]]} ;; -> (+ x y 2)

;; Outer brackets can be omitted if the number of parameters to replace is only one
{:replace [0 x]}  ;; -> (+ x 1 2)

[baku89]

And I rewrote some of the core functions with new syntax FYI

9bd6ff6