Added async versions of ODataClient main methods.
Added async versions of ODataClientWithCommand.
Merge branch 'master' into async

Conflicts:
	Simple.OData.Client.Core/Extensions/WebRequestExtensions.cs
	Simple.OData.Client.Core/Simple.OData.Client.Core.csproj
Finalized async methods.
Merged with master.
Merged with master.
Merge branch 'master' into async

Conflicts:
	Simple.OData.Client.SL5/Simple.OData.Client.SL5.csproj
Removed SL5 project.
Added strong type API definitions as dynamic alternatives.
FilterExpression refactoring.
Replaced DynamicObject inheritance with IDynamicMetaObjectProvider.
Added DynamicFilterExpression.
Implemented typed filter expressions.
Fix in Droid test.
Fixed stack overflow error in Linq expression parser.
Added missing expression operators.
Added iOS PCL and solution.
Moved dynamic API to Simple.OData.Client.Dynamic.
Fixed different GetPrefixOfNamespace behavior on Win and Android.
Updated NuGet packages.