[web] fix app.isApplet() method

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24943 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
HTML5: shift needed for wheel zoom
Java: remove Ctrl for wheel zoom (also zooms browser page)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24944 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
for applets: allow buttons to be dragged only if the button tool is selected (important for tablets)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24945 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Avoid repainting the label too often

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24946 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e