Package docs-install_school_junior: Information

- remove docs-install-school from Provides/Obsoletes
- use hardcoded Name: in spec for better gear utilities support

- fix headings in netinstall section
- edited last step description
- add note to bootloader section
- some rephrasings
- replace 'ye' with 'yo' & typo fixes
- add bios boot priority settings note

- replaced wrong add_disks/packages/x11 screenshots
- fixed Version: in docinfo