Better GitHub issue and pull-request templates

[felixevers]

GitHub offers the useful option of issue and pull-request templates. In this project, it would be an advantage to have multiple distinc templates for different purposes. For example, an issue for a bug report should look different than an issue for a feature request.

In addition, these templates and everything else should be placed in the .github folder for a better overview.

Useful templates:

• [ ] bug report
• [ ] improvement
• [ ] enhancement
• [ ] testing
• [ ] blank issue
• [ ] pull request template

[lissyx]

We already have a template for bug report. I'm not sure we need all the other ones (what difference do you make between improvement and enhancement? what would testing cover? why a PR template?), but please feel free to send PR to explicit your point of view