Add csv data

[kruegert]

Add the possibility to register csv data to the lens and map x and y columns.
The csv data example: [ID, x_position, y_position, ... , ... , ...]

Show values:
When the user hovers over a certain x and y position in the image and one row in the csv file is within the lens, we want to show the value next to the lens. Later this could be in some visual form. For now, we could have just the raw value output.
For a quick lookup in the csv data you can use a quadtree structure: https://www.npmjs.com/package/data-tree

Here is a sketch of how that could look like:

The registration of a csv file should be optional and user should be able to specify x and y columns and later on how the values are displayed (text as in image, or grahpical with bars, histograms, etc.)

[jessupjs]

Update: CSV / JSON support in progress - currently able to bring in color objects for data_rGB filter.