v1.0.5 : support non default solution file struct

non default solution struct : <solutionDir>\anyDir\<projectDir>
can be build with: msbuild /p:SolutionDir=<solutionDir> hoge.csproj

if SolutionDir is *Undefined* :  SolutionDir is defined to ProjectDir\..
(default solution-project relation )
v1.0.6: Supports SDK+MBT

fix not found 'Microsoft.Build.Tasks.v4.0.dll' on SDK+MBT build
environment
use v12 for if exists Microsoft.Build.Tasks.v12.0.dll
v1.0.6 update nuspec