Django experiments/Results table could be largely simplified

Currently, our Results table contains 4 columns that store data types: one for integers, one for floats, one for booleans and one for "everything else". In order to know how to read the data, the platform consults the value of the "type" column" and then reads the corresponding field, with an adequate de-serializer.

In order to support the new plotting standard, the choice of implementation would be to add a "type" field on chart data (saved at the "Data value" column), which implies in a hack to ignore such a field on beat.core.

The way to solve this cleanly could go through:

1. Re-write the Result table so that all results are represented by strings or binary blobs
2. Condition the readout of Result tables to the type of the data object, as defined in the "type" column, which would have to be set to a "string" type.

This technique would remove 3 columns from the table, simplifying it, at the cost of reviewing the code that uses/displays results.

Because all results would be expressed into string (or binary), no need to worry about issue #83 (closed) anymore, would this solution be taken.