Fixes issue 4
Rebased off of host master to reduce the chance of a merge conflict
* rdpsign.vb: updated to dynamically determine the path to rdpsign.exe
* rdpsign.vb: updated to show an error if rdpsign.exe cannot be found (now imports system.windows.forms for MessageBox)
* Create Client Connection window: Made some visual + text changes
* Create Client Connection window: Disable the signing section if rdpsign.exe not detected or if no certificates are found
* Create Client Connection window: Change "Disabled" checkbox text to "Sign RDP file" and reverse its logic (so that checked = sign rdp file)
* Create Client Connection window: "Create Signed and Unsigned" checkbox is disabled + unticked if generating an MSI
* Create Client Connection window: Certificate ComboBox defaults to the first certificate rather than blank
* Create Client Connection window: Updated the save/reset settings to include the new signing section
* Create Client Connection window: Updated the Tab-Order
Fix Issue 4
* Added in library for signing the generated RDP file
* Library requires the certificate to have a friendly name for it to show up in the drop down. No friendly name, no certificate in dropdown
* Library detects the rdpsign.exe version to determine proper arguments (/sha1 or /sha256)
* Updated RemoteApp Tool to use new library and sign the RDP file after it is created
* Added in logic around the signing to prevent editing after creating the RDP file if signed
* Library allows for creating an unsigned backup along with the signed version, added ability to do the same in RemoteApp Tool
* Updated RemoteApp tool to use Visual Studio 2019, but allows for support back to some pervious versions
* Tested on Windows 10 and Windows Server 2008 R2 and was successful on both
