[GH-539] Add dataset for floating point columns

[prtkgaur]

Add dataset needed for testing performance of floating point values.

[prtkgaur]

Add dataset needed for testing performance of floating point values.
Files are in csv format, I did this for easier testing. Let me know if the you (the reviewer thinks otherwise).

[emkornfield]

Thanks for the PR:

1. Lets finalize on the spec changes first (I think there is still some easy room for reducing size).
2. Lets at least have two simple examples, where the content is well defined that covers the following cases:
   a. Null values
   b. 0 Exceptions for blocks
   c. 1 exception for a block
   d. >1 exception for a block.
   e. A block with all exceptions.
   f. differning exponent/value per block.

(are there other data variations that are important to cover?)