Refactor project.json dependencies

The packages are now dependencies of the `dnxcore50` framework itself,
rather than globally. The `compilationOptions` were pruned, with
`CORECLR` moved to frameworks, `_CORECLR` removed for all but
`Management.Infrastructure`, and `LINUX` moved to a new `Linux`
configuration, used only in `build.sh`. This configuration is
purposefully absent from libraries that do not use `LINUX`, so that it
is not relied upon without strong consideration. The dependencies
were pruned to reduce duplication.

build.sh

@@ -37,7 +37,7 @@ mkdir -p $BIN/Modules
 # Publish PowerShell
 (
     cd src/Microsoft.PowerShell.Linux.Host
-    dotnet publish --framework dnxcore50 --output $BIN
+    dotnet publish --framework dnxcore50 --output $BIN --configuration Linux
     # Temporary fix for dotnet publish
     [[ -d $BIN/Debug/dnxcore50 ]] && cp $BIN/Debug/dnxcore50/* $BIN
     # Copy files that dotnet-publish does not currently deploy