Add PXC and replication features

* Add `--change-master-options` (Issue datacharmer#107)
* Add more tests
* Docker test now downloads latest 8.0 binaries instead of using built-in.
* Improve PXC handling of defaults across versions
* Fix defaults for PXC 5.6, which were broken after introducing support for PXC8.0 (Issue datacharmer#106)

Use env instead of bash path in shell scripts

Change all explicit bash paths in shell scripts to 'env bash'

Add ability to deploy PXC 8.0 out of the box

dbdeployer deploys PXC 8.0 without need to add any options
(using `wsrep_sst_method=rsync` for 5.7 and `wsrep_sst_method=xtrabackup-v2` for 8.0)

Add custom user management

* Add option --task-user and --task-user-role to create additional user with custom role.
* Add cookbook recipe single-custom-users (include sample creation of orchestator user)
* Add test for cookbook scripts
* Add code security checks

Improve 'global' and 'downloads' commands

* Add custom role to 8.0 sandboxes
* Add role related options: --default-role, --custom-role-name, --custom-role-privileges,
  --custom-role-target, --custom-role-extra
* Add filters to global command:
  --type, --flavor, --version, --short-version, --name, --port, --port-range.
  Each option can also be negated (--type='!single', --flavor=no-mysql, --port='!8019')
* Add verbose and dry-run flags to global.
* Add metadata_all_template script to composite sandboxes
* Add command downloads add
* Add tarballs for 5.7.29, 8.0.19 for MySQL and NDB (Linux and MacOS)

[skip ci] Update CHANGELOG.md

[skip ci] Update CHANGELOG.md

[skip ci] Update CHANGELOG.md

update docs

update docs