workaround for some REPORT / STOP BLOCK issues

enables reporting and stopping a bock from within a C-shaped slot in a
custom block, but not (yet) out of nested C-shaped custom blocks (but
that’s coming up, too)
fixed #599

disable IDE keyboard shortcuts in presentation mode
add localization to default costume name
add localization to default project name
correct errors in Portuguese translation and add translated strings
fixed #601

correctly display symbol for %obj type input slots in the prototype
template
Merge pull request #600 from MMSequeira/master

Corrections and additions to Portuguese translation
updated history
New feature - minimal stage mode (shift-click on small-stage button)
fixed #604. Thanks, @Gubolin!