Evaluate Condition each Import within ImportGroup.
skip Condition and ContinueOnError as task parameters. Do not use null toolsVersion as is in IBuildEngine2 implementation.
Unlike MS.Build.Engine, sln files cannot be supported in MS.Build.dll, so deal with them in this tool.

Conflicts:
	mcs/tools/msbuild/Main.cs
	mcs/tools/msbuild/SolutionParser.cs
BuildEngine4 must not be reused as IBuildEngine when building another project by <MSBuild> task. Set current directory.
several fixes to load get buildable Project and run working builds.
Fix mobile builds.
Revert "Remove private sln/csproj files."

I need these projects while I'm hacking MSBuild.

This reverts commit f188c158d4643804e1fbece996fe535344fe9450.
Add experimental "MSBuild.exe" implementation which is based on Microsoft.Build.dll.

Conflicts:
	mcs/tools/msbuild/Main.cs
	mcs/tools/msbuild/SolutionParser.cs
Update .csproj (to add MSBuild.csproj).
update .sln too.
Add logger related tests (to sort out those Loggers properties relationship)
rename some use of "xbuild" to "msbuild". Give loggers to ProejctInstance.Build() as expected.
Add test for DefaultTargets handling with imports.
Use ProjectInstance's DefaultTargets which also covers imports.
skip Condition and ContinueOnError as task parameters. Do not use null toolsVersion as is in IBuildEngine2 implementation.

Conflicts:
	mcs/class/Microsoft.Build/Microsoft.Build.Internal/BuildEngine4.cs
Unlike MS.Build.Engine, sln files cannot be supported in MS.Build.dll, so deal with them in this tool.
BuildEngine4 must not be reused as IBuildEngine when building another project by <MSBuild> task. Set current directory.
several fixes to load get buildable Project and run working builds.
Merge branch 'msbuilddll2' of https://github.com/atsushieno/mono into msbuilddll2

Conflicts:
	mcs/tools/msbuild/ErrorUtilities.cs
	mcs/tools/msbuild/Main.cs
	mcs/tools/msbuild/Parameters.cs
	mcs/tools/msbuild/SolutionParser.cs