Update Che 7 known issues:
https://www.eclipse.org/che/docs/che-7/introduction-to-eclipse-che/#che-7.0-known-issues

• bump version to 7.1
• check with Ilya B. whether any issues need to be added (the ones present from 7.0 all remain)

(Apologies, this slipped my mind, so it's now late. The sooner it's updated, the better.)