* executor: move local specific git initialization out of base
* machine: return kwargs for executor init instead of executor object
* executor: add initial ssh executor
* ssh-executor: disable strict host checking for dvc-machine instances
* initial tests for ssh executor
* drop GIT_SSH_COMMAND usage
* push: accept destination odb as a parameter
* separate cache initialization into executor.init_cache
* add test for ssh executor cache init
* remove dead code
* machine: fixture-ize default test scenarios
* test SSHExecutor.from_machine
* tpi: return default SSH port for constructing executors
