Adding AQSOL Dataset

[rbSparky]

(Related to issue #239) Reference: pytorch geometric

The AQSOL dataset from the Benchmarking Graph Neural Networks paper based on AqSolDB, a standardized database of 9,982 molecular graphs with their aqueous solubility values, collected from 9 different data sources.

Will add tests.

[rbSparky]

Tests to be added(and docstring)

[rbSparky]

Works locally with path hardcoded, while downloading it gets stuck on "do you want to download [y/n]" any suggestions?

EDIT: figured it out ENV["DATADEPS_ALWAYS_ACCEPT"] = "true"

[rbSparky]

Works locally, will check here now

[rbSparky]

For some reason can't see the tests here(the ones that failed aren't loading). @CarloLucibello do you see any obvious issues that I need to fix here?

EDIT: Fixed

[rbSparky]

Tests pass, will add more tests and docs

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 96.15385% with 1 line in your changes missing coverage. Please review.

Project coverage is 44.83%. Comparing base (3d40a68) to head (d7c8214). Report is 4 commits behind head on master.

Files	Patch %	Lines
src/datasets/graphs/AQSOL.jl	95.83%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #240 +/- ## ========================================== - Coverage 45.94% 44.83% -1.11% ========================================== Files 50 51 +1 Lines 2501 2516 +15 ========================================== - Hits 1149 1128 -21 - Misses 1352 1388 +36 ```

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[CarloLucibello]

AQSOL should be added to the documentation in docs/src/datasets/graphs.md

[rbSparky]

All changes have been made