Rename CLI

[jensmueller-com]

This pull request contains the following breaking changes:

General changes

• Rename "Db2 Data Gate CLI" to "IBM Cloud Pak Operations CLI"
• Rename data-gate-cli distribution package to cloud-pak-operations-cli
• Rename dg_plugins entry point group to cloud_pak_operations_cli_plugins
• Rename dg console script to cpo
• Rename dg package to cpo
• Rename CLI data directory from ~/.dg to ~/.cpo

CLI command name changes

• Rename cpd3 install_cloud_pak_for_data command to cpd3 install

Class & method name changes

• Rename BinariesManager.get_dg_binaries_file_path() to get_binaries_file_path()
• Rename ClusterCredentialsManager.get_dg_clusters_file_path() to get_clusters_file_path()
• Rename DataGateConfigurationManager.get_dg_bin_directory_path() to get_bin_directory_path()
• Rename DataGateConfigurationManager.get_dg_credentials_file_path() to get_credentials_file_path()
• Rename DataGateConfigurationManager.get_dg_directory_path() to get_cli_data_directory_path()
• Rename DataGateConfigurationManager class to ConfigurationManager

Db2 Data Gate-specific changes

• Move commands specific to Db2 Data Gate to separate distribution package (plugins/cloud-pak-operations-cli-db2-data-gate)
• Remove aspects specific to Db2 Data Gate from documentation