Update issuetemplate.php
Update issuetemplate.php

Made some changes according to the previous discussion. Also made some further improvements reducing the need of scrolling.

- Divided Server configuration into two parts, General and Nextcloud
- Operating system, webserver etc. are back to using only one line
- Removed headings to `detail`-blocks, they already have a name, saved some space and rearranged the order a bit.

Looking forward to your input about these changes.
juliushaertl/issuetemplate,juliushaertl/issuetemplate