Dimcli

* Added DSL grammar for DSL V2.6

* New parameters for [DslDataset.as_dataframe()](https://digital-science.github.io/dimcli/modules.html#dimcli.core.api.DslDataset.as_dataframe)
* Improvements to the `--nice` and `--links` rendering of dataframes with Dimensions data
- with hyperlinks, drop IDs if title is present
- affiliations as a list with GRID links
- generic 'default_transform' method for extra column not in transformations
* Test suite for magic commands
* New feature: `verify_ssl` option for `login()` method

* Fix bug with df_grant_investigators_affiliations methods
* `dim_utils.dimensions_styler`: format the text display value of a dataframe by including Dimensions hyperlinks whenever possible.
* `dim_utils.converters`: JSON converters utils allow to pass a dataframe and get back an altered version of it where complex structures are transformed into list of comma separated values.
* Magic commands: refactoring of line/cell operations
* Variable name can be passed to save data
* `--links` parameter: makes resulting dataframe table interactive
* `--nice` parameter: convert struct to strings for easier reading and export
* `dsldocs` can be used as a cell command too

* Fix compatibility issues with DSL V2
* Grants field: `investigators_details` => `investigators`
* Added DSL grammar for DSL V2.1

* Installation package updated so that `requirements.txt` gets added to distribution
* So to fix Conda installation [ISSUE-75](https://github.com/digital-science/dimcli/issues/75)
* Merged [PR-76](https://github.com/digital-science/dimcli/pull/76) adding `MANIFEST.in` file

* Bug fix: automatic login token refresh breaking in certain cases
* Bug fix: CLI not printing out JSON data correctly due to conflicting metadata keys ('_copyright')
* Bug fix: CLI export_gsheets command not working correctly