added code to update warning and error counts when blocks are removed

Change-Id: I28d858bfb09470cfa66ef2afe9228ee48e105b43
Permit People to Continue Past Double Session Warning.

Add a third option to the dialog box to permit people to continue
working even though there is a second account logged in. This will
permit classes that use one ID to continue to work. It should be OK as
long as two people do not work on the same project.

Change-Id: Iaaeb7afeea36cc0820cb12f75a282f6d8cccdec5
Names in the media box are truncated in the middle

We were truncating at the end of the file name, but that makes certain files
hard to distinguish (longNamedImage_1.png and longNamedImage_2.png).
The Finder in OSX truncates in the middle, and that was the suggested model.

Change-Id: I49bd25c81c522ee053d38d1290468668634a4dad
Merge branch 'master' of https://github.com/mit-cml/appinventor-sources
Merge branch 'privacyinformer'