Better project files.

- Output directly to rel\ instead of to bin\ and then copying files over.
- Deduped Win32 vs x64 configs
- Moved some common properties to hexchat.props
- All build intermediates (except htm's intermediates) are no longer emitted in the source directory

src/fe-gtk/fe-gtk.vcxproj.filters

@@ -182,7 +182,7 @@
     <ClCompile Include="xtext.c">
       <Filter>Source Files</Filter>
     </ClCompile>
-    <ClCompile Include="resources.c">
+    <ClCompile Include="$(HexChatLib)resources.c">
       <Filter>Source Files</Filter>
     </ClCompile>
     <ClCompile Include="plugin-notification.c">
@@ -198,7 +198,7 @@
     </Manifest>
   </ItemGroup>
   <ItemGroup>
-    <ResourceCompile Include="hexchat.rc">
+    <ResourceCompile Include="$(HexChatLib)hexchat.rc">
       <Filter>Resource Files</Filter>
     </ResourceCompile>
   </ItemGroup>