Add capability to set the configuration

[LIQRGV]

The configuration needed to write to GCS.
Usually it's been on core-site.xml, but this PR allow us to write it on the code.

[jbonofre]

Thanks, much appreciated. Now that I did the 2.1.0.RC3 release, I will switch back on the IO PRs ;)

[LIQRGV]

This pull only add configuration for the writer.
I will investigate how to add that on reader.
:)

[LIQRGV]

Now the reader can using configuration too.

[LIQRGV]

Here is the example of the configuration:

gsConfig = new Configuration();
gsConfig.setClass("fs.gs.impl", GoogleHadoopFileSystem.class, GoogleHadoopFileSystem.class);
gsConfig.setClass("fs.AbstractFileSystem.gs.impl", GoogleHadoopFS.class, GoogleHadoopFS.class);
gsConfig.setStrings("fs.gs.project.id", StorageOptions.getDefaultInstance().getProjectId());

[jbonofre]

It seems you changed all files (without always modification). Can you please create a clean PR with only the diff ? Thanks !

[LIQRGV]

I've create a new branch with same name and delete the old one.
Could you review it ?
Or should I open a new PR ?

[jbonofre]

Absolutely. Thanks !