Improvements for MyRWDatasets and DatasetList components

[pablopareja]

Overview

This PR includes the following fixes and improvements:

• The component uses now the right service services/dataset instead of the old approach to handle datasets fetching and deletion as part of the MyRW --> datasets section
• WRISerializer is used now to convert the results from the requests to the appropriate JSON format
• Pagination toolbar is only shown when there are two or more pages of data
• Fix for a bug that prevented successfully loading the user datasets after one dataset had been removed

Testing instructions

Go to http://localhost:9000/myrw/datasets/my_datasets

Pivotal task

[agnlez]

@pablopareja feel free to merge.