Build glfw from source

[thomakra]

Based on #4 and GH-3, this change uses the Ubuntu 16.04 based nvidia-docker image and builds glfw.
I don't know what parts of ArrayFire actually depend on glfw, nor how you usually go about testing the Docker container.
Maybe you can shed some light on this, @pavanky or @mlloreda?
At least the build succeeds on my machine and I'm able to run the basic tests as described in Running Container:

$ ./build/test/backend_unified
Running main() from gtest_main.cc
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from BACKEND_TEST
[ RUN      ] BACKEND_TEST.Basic

Running Default Backend...
ArrayFire v3.4.2 (CUDA, 64-bit Linux, build 2da9967)
Platform: CUDA Toolkit 8, Driver: 375.26
[0] GeForce GTX 750 Ti, 1993 MB, CUDA Compute 5.0
Active Backend Enum = AF_BACKEND_CUDA

Running CPU Backend...
ArrayFire v3.4.2 (CPU, 64-bit Linux, build 2da9967)
[0] Intel: Intel(R) Xeon(R) CPU           W3550  @ 3.07GHz, 7965 MB, Max threads(8)
Active Backend Enum = AF_BACKEND_CPU

Running CUDA Backend...
ArrayFire v3.4.2 (CUDA, 64-bit Linux, build 2da9967)
Platform: CUDA Toolkit 8, Driver: 375.26
[0] GeForce GTX 750 Ti, 1993 MB, CUDA Compute 5.0
Active Backend Enum = AF_BACKEND_CUDA

Running OpenCL Backend...
ArrayFire v3.4.2 (OpenCL, 64-bit Linux, build 2da9967)
[0] NVIDIA  : GeForce GTX 750 Ti, 1992 MB
Active Backend Enum = AF_BACKEND_OPENCL
[       OK ] BACKEND_TEST.Basic (2026 ms)
[----------] 1 test from BACKEND_TEST (2027 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (2027 ms total)
[  PASSED  ] 1 test.

[pavanky]

@thomakra If it is linking fine, then that is totally ok :)

[pavanky]

@mlloreda Hmm, I just noticed that arrayfire is being run with graphics disabled. If that was the case then there is no reason to build GLFW or build arrayfire with graphics.

Any reason why the library was built with graphics support when it was being disabled at a later point ?

[mlloreda]

@pavanky we decided to leave it as an option for the user to compile and run with graphics. As a result, the respective flags were exposed in the Dockerfile to convey this information.

[mlloreda]

Thank you for the excellent PR, @thomakra!