fixed #277, #279 (blitting null-canvasses fails)

Thanks, Nathan, for the pointer to this!
null-canvas blitting bug follow-up
fix #275 #237; implements watchers for mouse x and mouse y
Merge pull request #282 from cycomachead/watcher

fix #275 #237; implements watchers for mouse x and mouse y
fixed saving/loading of new mouse coordinate watchers
Initial stop others block
adding libraries to the repo
Add useful headers to HTTP block
support for TELL and ASK

The FOR reporter’s first input now also accepts blocks and scripts
(„rings“), and reports a copy that is bound to the sprite indicated by
the second input. This lets you „zombify“ (or remote-control) sprites
(and create custom TELL and ASK blocks)
initial support for „sensing“ sprite-only custom block definitions

commented out for now
add mouseLeaveDragging() behavior to the paint editor, thanks, Kartik!

All credit for fixing this goes to Kartik. This also seems to change
just about every line ending for reasons known only to Xcode. Sorry
Kartik, for not pulling your request because of those line endings,
they are inevitable!
Only shrink-wrap sprite costumes

thanks, Kartik, for this fix!
Merge pull request #295 from blob8108/xhr-headers

Add useful headers to HTTP block
Merge pull request #283 from Hardmath123/master

Initial stop others block
fixed StopOthers blocks and added another option

also updated the German translation
updated history
Merge pull request #289 from cycomachead/lib

adding libraries to the repo
Collapse STOP primitives into a single block with a dropdown of options
German translation update for new (migrated) STOP block
Fixed Morphic updateReferences()

how could this go undetected so long? :-)