Add support for deploying content files

Resolves #125 

 - when doing an update, all files under **content** in the package are also added to the application directory
 - added test for "content is included in release package"
 - added test for "content is included when doing an install"

@peters - couple of questions

 - is including the content in the same directory as the executables what you were expecting?

TODO: 

 - [ ] test that content in subdirectories is brought across in the same structure