Install our Qt DLL directories recursively.

Qwindows.dll at least needs to be in the "platforms" subdirectory. Use a
PowerShell script to convert the output of windeployqt to its equivalent
NSIS instructions. Give the Qt DLL manifest a .nsh extension. Make sure
we uninstall known Qt DLL directories. DLLs now load correctly according
to Dependency Walker.

Install and uninstall our .qm files while we're here.

Change-Id: I06ed279809e6fce0e008c5f278a56b1ae34c8f21
Reviewed-on: https://code.wireshark.org/review/3267
Reviewed-by: Gerald Combs <gerald@wireshark.org>