Adds xml-doc output/packaging - fixes (#103)

Motivation:
Improve dev exp using DotNetty nuget packages.

Modifications:
- enabled xml-doc output on projects

Result:
xml-docs are packages along binaries in nuget packages.

src/DotNetty.Buffers/DotNetty.Buffers.csproj

@@ -30,6 +30,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <CheckForOverflowUnderflow>false</CheckForOverflowUnderflow>
+    <DocumentationFile>bin\Release\DotNetty.Buffers.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Signed|AnyCPU'">
     <OutputPath>bin\Release\</OutputPath>
@@ -39,6 +40,7 @@
     <PlatformTarget>AnyCPU</PlatformTarget>
     <ErrorReport>prompt</ErrorReport>
     <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+    <DocumentationFile>bin\Release\DotNetty.Buffers.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />

src/DotNetty.Codecs.Mqtt/DotNetty.Codecs.Mqtt.csproj

@@ -28,6 +28,7 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <DocumentationFile>bin\Release\DotNetty.Codecs.Mqtt.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Signed|AnyCPU'">
     <OutputPath>bin\Release\</OutputPath>
@@ -37,6 +38,7 @@
     <PlatformTarget>AnyCPU</PlatformTarget>
     <ErrorReport>prompt</ErrorReport>
     <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
+    <DocumentationFile>bin\Release\DotNetty.Codecs.Mqtt.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />

src/DotNetty.Codecs/DotNetty.Codecs.csproj

@@ -28,6 +28,7 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <DocumentationFile>bin\Release\DotNetty.Codecs.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />

src/DotNetty.Common/DotNetty.Common.csproj

@@ -129,6 +129,7 @@
     <CodeContractsRuntimeCheckingLevel>Preconditions</CodeContractsRuntimeCheckingLevel>
     <CodeContractsReferenceAssembly>%28none%29</CodeContractsReferenceAssembly>
     <CodeContractsAnalysisWarningLevel>0</CodeContractsAnalysisWarningLevel>
+    <DocumentationFile>bin\Release\DotNetty.Common.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Signed|AnyCPU'">
     <OutputPath>bin\Release\</OutputPath>
@@ -139,6 +140,7 @@
     <ErrorReport>prompt</ErrorReport>
     <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
     <WarningLevel>4</WarningLevel>
+    <DocumentationFile>bin\Release\DotNetty.Common.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />

src/DotNetty.Handlers/DotNetty.Handlers.csproj

@@ -28,6 +28,7 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <DocumentationFile>bin\Release\DotNetty.Handlers.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />

src/DotNetty.Transport/DotNetty.Transport.csproj

@@ -30,6 +30,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <RunCodeAnalysis>false</RunCodeAnalysis>
+    <DocumentationFile>bin\Release\DotNetty.Transport.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Signed|AnyCPU'">
     <OutputPath>bin\Release\</OutputPath>
@@ -41,6 +42,7 @@
     <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
     <WarningLevel>4</WarningLevel>
     <RunCodeAnalysis>false</RunCodeAnalysis>
+    <DocumentationFile>bin\Release\DotNetty.Transport.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />