#443 Various small documentation updates for 6.0

[Jean-Christophe Helary]

Various small documentation updates
- add translation conflict resolution section
https://sourceforge.net/p/omegat/documentation/429/
- Reference to access tokens
https://sourceforge.net/p/omegat/documentation/423/
- Add information about language codes, and format reference.
https://sourceforge.net/p/omegat/documentation/421/
- Segmentation rules file name is now segmentation.srx
https://sourceforge.net/p/omegat/documentation/428/
- Add warning about creating a project on a network drive
https://sourceforge.net/p/omegat/documentation/418/
- Remove "temporarily" from Editor > Enter new segment option.
- fix duplicate "ID" in XML set
https://sourceforge.net/p/omegat/documentation/419/

[Jean-Christophe Helary]

https://github.com/omegat-org/omegat/pull/1266