Upgrade all projects to target .NET Framework 4.5.2

In the advanced build settings, Language version was also upgraded from C# 5.0 to C# 6.0. The minimum Visual Studio version required will now be VS2015.

Algorithm.Python/QuantConnect.Algorithm.Python.csproj

@@ -9,9 +9,10 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>QuantConnect.Algorithm.Python</RootNamespace>
     <AssemblyName>QuantConnect.Algorithm.Python</AssemblyName>
-    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <LangVersion>5</LangVersion>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -21,6 +22,7 @@
     <DefineConstants>DEBUG;TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -29,6 +31,7 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <Content Include="CustomChartingAlgorithm.py">
@@ -50,7 +53,9 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <ItemGroup>
-    <None Include="app.config" />
+    <None Include="app.config">
+      <SubType>Designer</SubType>
+    </None>
     <None Include="build.sh">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>