Core: Refactor code for use within interactive environments

[vladsavelyev]

Moving towards the interactive use:

• Move the module report building logic out of __init__()
• Make Report a normal class instead of a module singleton

[ewels]

Wondering if we can add in logic here to check if the build() def exists within a module. If so then run it the new way. However, if it's not there, then run the old way with __init__().

This way, the change is not a breaking change and we can push the refactoring before v2.0, essentially as progressive enhancement. We can also use it as an opportunity to log depreciation warnings so that folks know that the new syntax is ready and should be switched to.

Things like lint tests can abandon the old syntax completely, as all core MultiQC modules should be using the new syntax immediately.

[ewels]

Outdated, replacement now merged 🚀