v2.7.0

- `New` Intermediate sized images for small screen devices #67
- `New` Added Docker help (@renfredxh, #252)
- `Improved` Upload shows server-errors
- `Improved` Improved thumb creation
- `Improved` Docker (@renfredxh, #252)
- `Improved` CSS has been rewritten partly
- `Improved` Front-end has been rewritten partly #245
- `Improved` Folder- and code-structure has been updated
- `Improved` Context-menu now based on [basicContext](https://github.com/electerious/basicContext) #245
- `Fixed` OpenGraph image too big for some sites #69
- `Fixed` Wrong sizes after EXIF rotation