Removing legacy versions of Visual Studio 2010 and 2012
IterationProxy for controlled access to embedded containers.
Switch access to SystemBody::m_children to IterationProxy interface.
Switch access to Space::m_bodies to IterationProxy interface.
Switch access to Frame::m_children to IterationProxy interface.
Switch access to UI::Container::m_widgets to IterationProxy interface.
Switch access to Lang::Resource::m_strings to IterationProxy interface.
Merge branch 'master' of https://github.com/pioneerspacesim/pioneer into remove-vs2012

Conflicts:
	win32/vc2012/graphics/graphics.vcxproj
	win32/vc2012/graphics/graphics.vcxproj.filters
Merge pull request #2772 from fluffyfreak/remove-vs2012

DISCUSS - Removing Visual Studio 2010 and 2012
Updated COMPILING.txt to remove 2008, 2010 and 2012 references to Visual Studio products.
Also update the changelog
Merge pull request #2784 from fluffyfreak/update-compiling

Merging
Merge branch 'iteration_proxy'
Automatically manage the cancellation of jobs with RAII.
Avoid calling JobClient::RemoveJob from ~JobHandle, as that means it *is* just being removed.
Update dependencies in premake4.lua, add release-symbols option
Merge pull request #2758 from lwho/job_auto_cancel

Merged (#2758)
Update Changelog.txt