Initial PR: Add gitignore and improve template detection

[gagb]

Why are these changes needed?

I am trying to address #1478 but we need to make some fixes to make it easy to collaborate on the AutoGenBench code.

This PR

• adds a gitignore to ignore Dowloads and Tasks in scenarios and Results in cwd
• generalizes init_tasks.py to detect all templates present in Templates

I will progressively make more comprehensive PR for long context management after this PR merge goes well, e.g., via a new template that uses hooks/capabilities

Why are so many folders using capitalized names??

Related issue number

#1478

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[gagb]

I will need help to resolve the formatting issue on this branch... Presumably because this branch is using a different pre-commit than what GH uses? @afourney might wanna update your dev branch to latest.

[afourney]

@gagb If you can figure out why this branch has pre-commit issues, you will be my savior and I will forever be in your debt. This is exactly why I filed #1418. It should be up to date with main as of this morning.

I like where this commit is going. I will review and probably merge it tonight after testing.

As for folder naming, I opened an issue to discuss this as far back as December #976. It was only recently that it seems to have ruffled any feathers (see #1424). There's an issue to possibly address it, but it's actually quite a lot of work. Like a lot of work. None of these are python modules, so I didn't apply python module naming rules (which I dislike). Where I am building python modules (e.g., the autogenbench sub folder), casing follows that convention.