[WIP] SnpEff: update version 5.1

[gallardoalba]

FOR CONTRIBUTOR:

• [x] - I have read the CONTRIBUTING.md document and this tool is appropriate for the tools-iuc repo.
• [x] - License permits unrestricted use (educational + commercial)
• [ ] - This PR adds a new tool or tool collection
• [x] - This PR updates an existing tool or tool collection
• [ ] - This PR does something else (explain below)

[wm75]

Cool. Have been working for a new release since quite a while!

[wm75]

@gallardoalba I will do an in-depth review next week. SnpEff is a complicated beast, but thanks for starting this.