Change naming convention, merge texture/shaders

Reduce the number of files in project by merging texture and shaders into
assets/renderer file. It's better to keep code local to where it is rather than
splitting them into "self-contained modules". It becomes easier to understand
reading top-to-bottom and there's is less jumping around which can increase the
difficulty of comprehending the code.

Convert names to use more of a <namespace>_<object><Action> format.

Dengine.vcxproj.filters

@@ -15,12 +15,6 @@
     </Filter>
   </ItemGroup>
   <ItemGroup>
-    <ClCompile Include="src\Texture.c">
-      <Filter>Source Files</Filter>
-    </ClCompile>
-    <ClCompile Include="src\Shader.c">
-      <Filter>Source Files</Filter>
-    </ClCompile>
     <ClCompile Include="src\Renderer.c">
       <Filter>Source Files</Filter>
     </ClCompile>
@@ -42,9 +36,6 @@
     <ClCompile Include="src\dengine.c">
       <Filter>Source Files</Filter>
     </ClCompile>
-    <ClCompile Include="src\UserInterface.c">
-      <Filter>Source Files</Filter>
-    </ClCompile>
     <ClCompile Include="src\String.c">
       <Filter>Source Files</Filter>
     </ClCompile>
@@ -57,6 +48,9 @@
     <ClCompile Include="src\Entity.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="src\Ui.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <None Include="data\shaders\default.vert.glsl" />
@@ -68,15 +62,9 @@
     <ClInclude Include="src\include\Dengine\Common.h">
       <Filter>Header Files</Filter>
     </ClInclude>
-    <ClInclude Include="src\include\Dengine\Shader.h">
-      <Filter>Header Files</Filter>
-    </ClInclude>
     <ClInclude Include="src\include\Dengine\OpenGL.h">
       <Filter>Header Files</Filter>
     </ClInclude>
-    <ClInclude Include="src\include\Dengine\Texture.h">
-      <Filter>Header Files</Filter>
-    </ClInclude>
     <ClInclude Include="src\include\Dengine\AssetManager.h">
       <Filter>Header Files</Filter>
     </ClInclude>
@@ -107,9 +95,6 @@
     <ClInclude Include="src\include\Dengine\WorldTraveller.h">
       <Filter>Header Files</Filter>
     </ClInclude>
-    <ClInclude Include="src\include\Dengine\UserInterface.h">
-      <Filter>Header Files</Filter>
-    </ClInclude>
     <ClInclude Include="src\include\Dengine\String.h">
       <Filter>Header Files</Filter>
     </ClInclude>
@@ -119,5 +104,8 @@
     <ClInclude Include="src\include\Dengine\Entity.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="src\include\Dengine\Ui.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>