BotService improvements

- If the issue is to do with Azure CLI 2.0 in-particular, create an issue here at [Azure/azure-cli](https://github.com/Azure/azure-cli/issues)

### Extension name (the extension in question)

botservice

### Description of issue (in as much detail as possible)

**Blocking**
- [x] `bot create`: kind needs enum value (https://github.com/Azure/azure-cli/blob/dev/doc/authoring_command_modules/authoring_commands.md#registering-enums)
- [x] `bot create`: Fix casing and help text. Group arguments (`arg_group` kwarg) and expose other options that the ARM template exposes. Consider adding an example.
- [x] Rename `bot get` command to `bot show`. (https://github.com/Azure/azure-cli/blob/dev/doc/command_guidelines.md#standard-command-types)
- [x] Rename ` get` commands to `channel show`. (https://github.com/Azure/azure-cli/blob/dev/doc/command_guidelines.md#standard-command-types)
- [x] for channels change `--enabled` to use three_state_flag and make not required (flag to disable) https://github.com/Azure/azure-cli/blob/dev/doc/authoring_command_modules/authoring_commands.md#registering-flags
- [x] Remove _ characters from option names.
- [x] Add missing help text. For "groups-mode" and "call-mode", use names that make it clear these are flags and not enums like "use-groups-mode" or "enable-groups-mode". https://github.com/Azure/azure-cli/blob/dev/doc/authoring_command_modules/authoring_commands.md#registering-flags

**Additive Changes**
- [ ] Support `--ids` for the bot service commands. https://github.com/Azure/azure-cli/blob/dev/doc/authoring_command_modules/authoring_commands.md#supporting-the-ids-parameter
- [ ] Expose `bot list` command.
- [ ] Consider exposing convenience arguments on the update command. https://github.com/Azure/azure-cli/blob/dev/doc/authoring_command_modules/authoring_commands.md#generic-update-commands
- [ ] * (for me) investigate whether --ids should apply or not for the channel commands.
- [ ] generic_update_commands for channel commands. https://github.com/Azure/azure-cli/blob/dev/doc/authoring_command_modules/authoring_commands.md#generic-update-commands

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