Windows: Build with VS2014

[wilhelmberg]

@springmeyer @brianreavis

I'm starting on migrating to VS2014/MSBuild14 right now.
Which branch should I work on? gdal-1.11.1?

Thinking about other projects using node-gdal, that are not yet up to VS2014, it might be useful to introduce a switch somewhere to build with VS2013 as default and with VS 2014 only if a special flag is passed.
What do you think?

[wilhelmberg]

Local compile is successfull, all 459 tests pass.

I've created a new branch (vc140) based on gdal-1.11.1.

I've created a new branch because I just realized that we need to compile against our own node.lib and the changes might be bigger than I thought.

[springmeyer]

Yes: we will need to compile and link against our own node devel headers/lib. Need to think about this more. Locally you can do this by passing --nodedir flag but ideally I can also come up with a node-pre-gyp solution to also be able to install from binaries and choose wither 2013 or 2014. Going to be. Tricky...

[springmeyer]

done in #77