vym: 2.6.11 -> 2.7.0 (#73483)

* vym: 2.6.11 -> 2.7.1

* vym: install man page

* vym: fix /usr paths and move data from $out/vym

* Change version to 2.7.0

There was some concern that the release tarball 2.7.1 actually contains an in-development snapshot rather than a full release. The consensus seems to be that 2.7.0 should be used instead.