M3-cli

* Fixed an error that removed attributes with `False` and `0` values in the JSON-view when the `nullable`
option was specified in the output configuration of the command (.e.g., `describe-instance` command).

* Refactored the code for interactive mode.
* Changed the format of dates to ISO 8601 in output of the following commands:
* activate-platform-service
* cost-object-report
* create-image
* create-schedule
* describe-events
* describe-images
* describe-platform-service
* describe-schedules
* describe-tenants
* resource-report
* subtotal-report
* total-report
* untagged-resource-report
* Changed the formatting of list attributes in output. Now, in table view list values are
aligned in column (one under another).

* Extended the response of the `describe-instance` command for `json` and `full` view, added `memoryGb`, `storageGb` and `cpuCount` fields.

* Changed the format of dates in output of the `terraform-describe-stack` command to ISO 8601.

* Shortened the description of `generate-platform-service-varfile` command.

* Unified response for `set-tag`, `delete-tag` and `describe-tag` commands.
* The `describe-service-section` and `delete-service-section` commands were implemented.