[Build-System] Remove Sofia-Sip library from the FreeSWITCH tree and use packages instead.

libs/win32/sofia/libsofia_sip_ua_static.2017.vcxproj

@@ -49,8 +49,10 @@
     <PlatformToolset>$(DefaultPlatformToolset)</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <Import Project="$(SolutionDir)w32\download_sofia-sip.props" Condition=" '$(downloadSofiaSipPropsImported)' == '' " />
   <Import Project="..\..\..\w32\gawk.props" />
   <Import Project="..\..\..\w32\openssl.props" />
+  <Import Project="$(SolutionDir)w32\sofia-sip.props" />
   <ImportGroup Label="ExtensionSettings">
   </ImportGroup>
   <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="PropertySheets">