exec task test

added a test to the exec task (grunt/exec.js) to check if the app/AppInspector/.sencha/ folder exists that is needed for the build
misc changes

#1 added an exec task (grunt/exec.js) test to check app/AppInspector/.sencha/ folder is present as it is needed for Sencha CMD build. - PLEASE RUN npm

#2 Re-added app/manifest.json placeholders (name & description).

#3 Added German manifest locales.