prevent undesired HTML5 dragstart event

(a new glitch introduced in Chrome 27)
Objects: fix for hiding 'getLastAnswer' and 'getTimer' primitives
BYOB: Newly created custom reporters now have an initial default REPORT block as definition body
Morphic: focus World canvas on mouse down (otherwise prevent default)
Code mapping

generating text code from blocks, first experimental iteration
Store: persisting code mappings

in project and block library files
GUI: make code mapping preference persistent
"flat" design enhancements for blocks and watchers
"flat" design enhancements for cells
Blocks: Multi-line input slots (TextSlotMorphs - %mlt)
Objects: doMapCode() primitive now uses a multi-line input slot
"flat" design: No rounded corners for watchers
Morphic, Blocks: "flat" design fix

Handle manually "unshadowed" StringMorphs without throwing an
exception. This lets you load the tools library into "flat" mode again.
%code input slot

multi-line, monospaced, type-in slot for code mappings
code mapping: pass on c-slot clode by default
code mapping: pretty printing support (work-in-progress)

commented out for now, not yet functional
Merge remote-tracking branch 'main/master'

* main/master:
  code mapping: pretty printing support (work-in-progress)
  code mapping: pass on c-slot clode by default
  %code input slot
  Morphic, Blocks: "flat" design fix
  "flat" design: No rounded corners for watchers
  Objects: doMapCode() primitive now uses a multi-line input slot
  Blocks: Multi-line input slots (TextSlotMorphs - %mlt)
  "flat" design enhancements for cells
  "flat" design enhancements for blocks and watchers
  GUI: make code mapping preference persistent
  Store: persisting code mappings
  Code mapping
  Morphic: focus World canvas on mouse down (otherwise prevent default)
  BYOB: Newly created custom reporters now have an initial default REPORT block as definition body
  Objects: fix for hiding 'getLastAnswer' and 'getTimer' primitives
  prevent undesired HTML5 dragstart event
pretty printing support for mapped code

better formatting capabilites now support Python mappings
code mapping: dialog input is now multi-line monospaced
fixed #100 saving costumes to the cloud