Ena-upload-cli

- Support for all optional and recommended fields for viral submissions based on the [ERC000033](https://www.ebi.ac.uk/ena/browser/view/ERC000033) checklist
- Support for empty values in optional and recommended fields (these will not be included in the final XML)

This release includes:
- Updated the XSD templates from [ENA](ftp://ftp.ebi.ac.uk/pub/databases/ena/doc/xsd) enabling correct local validations of the tables
- Updated XML templates to support new fields
- Replacing the `curl` dependency with the `requests` library from python (thank you mobilegenome!)
- `--version` option to print out the version of the tool

- Support for non mandatory columns in the viral sample table (Thanks tpall !)

- Better parsing of accession numbers and outputted in stdout in a tab separated manner
- Receipt is outputted as a receipt.xml file in the working directory
- Better handling of errors that do not produce a receipt
- Dropping support for python v2.X

- `--tool` option split in two: `--tool` TOOL_NAME default='ena-upload-cli' and `--tool_version` TOOL_VERSION default='0.2.5'
- `--tool` is not a mandatory option anymore
- tool_name and tool_version used for extra metadata fields in run, experiment, study and sample tables:

<RUN_ATTRIBUTES>
<RUN_ATTRIBUTE>
<TAG>SUBMISSION_TOOL</TAG>
<VALUE>${tool_name}</VALUE>
</RUN_ATTRIBUTE>
<RUN_ATTRIBUTE>
<TAG>SUBMISSION_TOOL_VERSION</TAG>
<VALUE>${tool_version}</VALUE>
</RUN_ATTRIBUTE>
</RUN_ATTRIBUTES>