Add neural network ( perceptron )

Add ARFF support.
Add mask feature.
Improve the output of various graphs.

Add MongoDB support
Add SQL Server support

The application has now its own icon :-)
Records can be permanently removed.
Improve bar graph output.
Improve line graph output.
Fix bug in box plot status.

Use Electron v0.35.6.
Terminate the application when the window is closed.
OSX : One can directly drop a file onto the application icon to process it.

Add capability to get the png image of a graph

Add BigQuery support

Fix bugs in histograms.
Improve box plot representation.

German translation of the help files, thanks to Mira Klein and Stephan Krauss.
Multi-line sql query allowed when loading data from mysql.

Detect numerical fields when importing from mysql.
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