Add "--browse" and "--input" to "arc paste", and remove "--json" (which had no effect)

Summary:
Ref T13528. For consistency with other commands ("arc upload", "arc diff"), support a "--browse" flag to "arc paste".

Support "--input" as a more robust alternative to x | y (see T6996).

Test Plan: Ran arc paste --browse --input X, got a new paste in a browser window. Ran other variations of flags and parameters.

Maniphest Tasks: T13528

Differential Revision: https://secure.phabricator.com/D21203