Change language on "mouse-pointer" blocks

Overview

Scratch 3.0 will work on a wide variety of devices including Chromebooks, Windows Surface, iPads, and Android tablets. Many of these devices either exclusively support touch or support a mixture of touch and mouse interaction. Because of this, we would like to retire use of the terms "mouse-pointer" and "clicked" and use the more generic terms "pointer" and "tapped". This will impact a large number of blocks, but feels important in order to properly support touch platforms moving forward.

Changes

Move

• go to (pointer)
• glide (1) secs to (pointer)
• point towards (pointer)

Events

• when this sprite tapped
• when stage tapped

Sensing

• <pointer down?>
• (pointer x)
• (pointer y)
• (distance to (pointer))

Details

• The (distance to (pointer)) block should be moved down to below the (pointer y) block. It's current positioning in the "Sensing" category doesn't make much sense (particularly for a block that isn't used very heavily).

Moved from LLK/scratch-vm#1015
/cc @thisandagain @speakkvisually @kenny2github

No files or tests are named; start by locating the block definitions and message/localization entries for the listed Move, Events, and Sensing blocks. Check the current labels and category ordering against the checklist, then verify that the mouse-specific terms are replaced consistently and the distance block is positioned below pointer y.