Finished multiple upload work (older: .NET framework and web site --> app)

- Finished implementation of the multiple upload work
    - Added security to the system by utilizing a security token in the session state
    - Added ability to filter the files by file extension, at both client and server
    - Now correctly works simulatenously in the same session
    - Implemented all options in the control, such as not allowing multiple etc..
    - Finished clean-up of old files
- Last version unreported major work (somehow I missed this)
    - Switched to ASP.net 4.5 Framework (no real changes introduced)
    - Converted from an ASP.net web site to an ASP.net web application (brand new solution)
    - VS2012 solution file now at the top-level named SobekCM_Web.sln