Enable nested vsprops

[theComputeKid]

vsprops was added in #2112 with the following API:

vsprops {
  Name1 = "value1",
  Name2 = "value2",
}

This is a useful addition. However, nested properties are not allowed, and only one level of properties can be added to the project XML. This change enables nested properties. This is useful for custom tooling/extensions for Visual Studio.

This is not a breaking change for the original behaviour, it only adds nested vsprops:

vsprops {
  Name1 = "value1",
  Name2 = {
     Name3 = "value3"
  }
}

Translating to:

<Name1>Value1</Name1>
<Name2>
  <Name3>Value3</Name3>
</Name2>

While editing the file, I took the opportunity to remove unnecessary harmless extra spaces from a few lines in modules/vstudio/vs2010_vcxproj.lua, my IDE formatted them.

• Focus on a single fix or feature; remove any unrelated formatting or code changes
• Add unit tests showing fix or feature works; all tests pass
• Mention any related issues (put closes #XXXX in comment to auto-close issue when PR is merged)
• Follow our coding conventions
• Minimize the number of commits
• Align documentation to your changes

[theComputeKid]

@Jarod42 It has been quite some time, can this be merged pleased?

[Jarod42]

@theComputeKid :I cannot merge, I don't have any rights on that repo. I'm like you, an external contributor...