Prepare GitHub templates for pull requests and issues

[sebbrudzinski]

GitHub offers a way for projects for defining templates, while creating pull requests and issues (see more info here: https://github.com/blog/2111-issue-and-pull-request-templates). The templates will be filled in the text boxes and may contain guidelines for contributors on what information to include with created pull request or how to properly report a bug / submit an enhancment issue. As a part of this ticket, we may also standardise the issues and pull requets creation.