Identify clauses.

What constitutes a clause is context dependent. In a map, it will be a
key/value pair. In a vector it will be a single element, unless the vector
establishes bindings as in `let`, in which case it will be a pair of elements.
This code tries to be aware of common functions, data structures and other
forms, and their conventions for establishing clauses.

It also tries to be aware of how comments are usually written in Clojure code.
It associates comments 'above' a clause and on the same line 'after' a clause
with the clause.

clojuredocs integration inspired on orchard implementation.

Drag clauses forward or backward.

{:a 1, :b 2} -> {:b 2, :a 1}

Though this feature was originally called 'move collection entry', it is now
more generally used to drag any clause forward or backward, even if it isn't
in an immutable collection.