Polysh

* Remove `--log-dir=LOG_DIR` option as it is less useful than expected
* Add `--log-file=LOG_FILE` option aggregating all remote shells
* Remove `--quick-sh` as it is now the default
* Replace the control shell with colon prefixed commands
* Make the prompt use readline even when not all remote shells are ready
* Forward `Ctrl-C`, `Ctrl-D` and `Ctrl-Z` to the remote shells
* Allow running local commands
* Add `:chdir` control command to change the local directory
* Add `:hide_password` control command, to use with `su(1)` for example
* Add `:reset_prompt` control command, for use when launching a shell
* Add `:replicate` and `:upload` control commands to do some file
transfer
* Add `:export_rank` control command to uniquely identify each shell
* Add `:show_read_buffer` control command to see what `gsh` just read
* Print help for common SSH key problems
* New completion from the local filesystem
* Simplify `:list` output, and added the last printed line

* Use readline to provide fancy command line edition and completion from
history
* Print incomplete lines after some delay
* Support dynamically adding/deleting/renaming remote shells
* New option `--quick-sh` to avoid launching a full blown session
* Add hostname expansion: for example `host<1-100>` and `host<001-100>`
* Add an option to read hostnames from a file
* Remove useless option to print only the first line of output
* Miscellaneous bug fixes and optimizations
* Add man page

* First release