This commit adds 6 new options to elixir CLI to aid releases:
* `--pipe-to PIPEDIR LOGDIR` - invokes run_erl with daemon pipe and logs (only on Unix-like systems)
* `--rpc-eval NODE COMMAND` - evaluates the given expression on the given node
* `--boot FILE`, `--boot-var VAR VALUE`, `--erl-config FILE` and `--vm-args FILE` - which are equivalent to Erlang's `-boot`, `-boot_var`, `-config` and `-args_file`
We have also rewritten the CLI to only pass Elixir options to Kernel.CLI.