Provide sample build systems

[springmeyer]

We should provide a standard/recommended build system. The idea is that people will start with the hello world plugin for developing other plugins.

The "standard/recommended" should be:

• gyp config that calls out to mapnik-config for most details
• should work as similar as possible on windows and unix
• should build against Mapnik 3.0.0 binary packages (until 3.0.0 release is available should use latest 3-dev SDK)

[mathisloge]

#4 would set the build system to cmake.