Docker upgrade

[marcorosa]

Upgrade the docker image used for the UI (use python3.9 instead of python3.7, now that it is supported)

[marcorosa]

Not every base image for Docker fully supports hyperscan package. In some of them, libhyperscan needs to be built from source (which would take a lot).
Ref

At this date, when trying to set the base version of docker image to python:3.9 in place of python:3.7:

...
credential_digger_sqlite |   File "/usr/local/lib/python3.9/site-packages/credentialdigger/__init__.py", line 1, in <module>
credential_digger_sqlite |     from .client import Client
credential_digger_sqlite |   File "/usr/local/lib/python3.9/site-packages/credentialdigger/client.py", line 13, in <module>
credential_digger_sqlite |     from .scanners.file_scanner import FileScanner
credential_digger_sqlite |   File "/usr/local/lib/python3.9/site-packages/credentialdigger/scanners/file_scanner.py", line 8, in <module>
credential_digger_sqlite |     import hyperscan
credential_digger_sqlite |   File "/usr/local/lib/python3.9/site-packages/hyperscan/__init__.py", line 5, in <module>
credential_digger_sqlite |     from hyperscan._hyperscan import *
credential_digger_sqlite | ImportError: /usr/local/lib/python3.9/site-packages/hyperscan/_hyperscan.cpython-39-x86_64-linux-gnu.so: undefined symbol: hs_compile_lit_multi

[marcorosa]

• Give a name to the images in the docker-compose.yml
• Update instructions in the wiki, in the page "How to update the project"