Docs/website: Add a maven pom file / project generator

@AlexDBlack commented on [Tue Aug 23 2016](https://github.com/deeplearning4j/deeplearning4j/issues/2028)

Spring initializer: http://start.spring.io/
That allows people to set up a project very quickly, even if they don't know maven. We could add something similar for DL4J.

How this would work for DL4J:
- Specify artifact ID etc
- Specify DL4J/ND4J version
- Specify nd4j native vs. cuda
- Tick boxes for optional dependencies: ui, nlp, spark, arbiter, etc.
then: "Generate Maven pom.xml" and "Generate SBT" etc buttons.

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@huitseeker commented on [Tue May 16 2017](https://github.com/deeplearning4j/deeplearning4j/issues/2028#issuecomment-301831849)

See also https://github.com/deeplearning4j/deeplearning4j/issues/1466

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@huitseeker commented on [Fri May 26 2017](https://github.com/deeplearning4j/deeplearning4j/issues/2028#issuecomment-304385673)

 [DataVec, workflow & al. - improve documentation](https://trello.com/c/3u3jt2lF/5-datavec-workflow-al-improve-documentation)