nuspec file.  not even close to being correct yet.  committing it as a checkpoint.
getting the NuGet stuff working (a task on which there is no actual progress so far) is requiring me to make the build stuff more, er, correct.  this commit reworks the builds of the SQLite C code, separating each platform into its own project file, using handwritten msbuild stuff to reduce duplication between all those nearly-identical project files, so that the building the SLN in visual studio actually builds everything we need.  there is more to be done here.  I only did the sqlite3 projects so far.  the cppinterop projects need a similar treatment.
Merge branch 'master' of https://github.com/ericsink/SQLitePCL.raw