Unify build paths in all MSBuild VS projects and extract common build
logic into functions.
Note that this change changes both VS2010 and VS2013 projects to have
more predictable output paths and fixed output file name (pugixml).
Put debugging information into the object file so that it can be shipped
with NuGet binaries. Based on the linker settings for the executable
debug info will either be put into the final .PDB or stripped out.
Fixes#110.