add ebuilds for dev-db/etcd* packages and updates for app-admin/fleet package

I'm not sure why the original ebuild author only picked some files of the documentation and generated man-pages. There is a lot more:
```
├── api.md
├── clients-matrix.md
├── cluster-discovery.md
├── clustering.md
├── configuration.md
├── debugging.md
├── design
│   ├── cluster-finding.md
│   └── standbys.md
├── development-tools.md
├── discovery-protocol.md
├── errorcode.md
├── etcd-file-system.md
├── img
│   └── etcd_fs_structure.jpg
├── internal-protocol-versioning.md
├── libraries-and-tools.md
├── modules.md
├── optimal-cluster-size.md
├── platforms
│   └── freebsd.md
├── production-ready.md
├── security.md
├── tuning.md
└── upgrade.md
```
I suggest skipping the man-page generation and use ```dodoc -r``` on the whole Documentation folder.