Fixes U4-2822 Datepicker throws "Specified cast is not valid" when saving through API
Creates IDisposeOnRequestEnd and ensures UmbracoContext and UmbracoDatabase implement it, then we only dispose of these types of objects at the end of the request if they are part of the httpcontext items (U4-2738). Fixes: U4-2988 UmbracoObjectTypesExtensions is not thread safe
Bump version number
U4-2709 Error after upgrading from 6.1.3 to 6.1.4
Fixes: U4-2925 Tree performance is very poor in 6.1.x when having event subscriptions
Obsoletes the LoadMinimalDocument flag since it no longer serves a purpose.
re-enables LoadMinimalDocument and adds this to the optimized check, even in optimized model the OnRenderNode can still execute with a minimal doc.
Fixes EditUser.aspx
fixes unit test
U4-2788 Error installing Umbraco 6.1.5 with SQL CE 4 option
NuSpec update: we can only accept a specific version of MySQL
Merge branch '6.1.6' into 6.2.0

Conflicts:
	build/Build.bat
	src/Umbraco.Core/Configuration/UmbracoVersion.cs
	src/Umbraco.Web.UI/Umbraco.Web.UI.csproj
	src/Umbraco.Web/umbraco.presentation/umbraco/users/EditUser.aspx.cs