fix #1074 build.cmd issues with spaces in repository paths
Fix #1073 - remove (unimportant) encoding edge case for data uri encoding (on asterisks) that changed between .net 4 and 4.5.  See bug for more details.
added missing curly brackets to HtmlHelperExtensions
Added toggle for download messages

When room is locked there is no UI to indicate that you cannot download
messages #1055

* Added new download icons
* Added toggleDownloadButton to Chat.ui.js
* Updated room methods to change button status on room change and lock
  change
Added keyboard support for paste upload dialog

Added support for <esc> and <enter> on the preview dialog for pasting images

* ESC: closes the dialog and stopping upload
* ENTER: uploads the file and closes dialog

Also focus to the chat box after closing.
Don't require restart after enabling/disabling content providers.