[updating] Updating a MISP instance

[SteveClement]

The current state of affairs when updating a MISP instance is less then ideal.
A lot gets skipped and inconsistencies between installed modules and expected modules are common.

Most deployments do manual upgrades of the various bits and pieces of their installations, but things might get missed.

The installer wants to have an option to check the current installation and whether some components need updating.

Here is an initial list of files that need to be checksummed and compared with a the current version:

$PHP_INI (check relevant options)
${PATH_TO_MISP}/venv (check python version)
Python Modules:
${PATH_TO_MISP}/app/files/scripts/[python-cybox,python-stix,python-maec,mixbox,cti-python-stix2]
pydeep, pylief, zmq, python-magic, plyara
PHP modules: redis, gnupg

Missing: misp-modules (this will be documented once the PR for enabling/disabling modules is merged)