Add command completion

[nimrod-a]

Add command completion #410

• Adds shell completion scripts for Bash and Zsh
• Adds documentation on activating command completion and on generating shell completions locally

For reference: Click Docs

Testing

For testing, you would need to either generate your own shell completion scripts or download the ones in this commit.
The Curl command in the docs would not work yet as the files are not available in the repo.

Note

As an alternative to providing the user with pre-generated shell completion scripts, one ca add the following to ~/.bashrc / ~/.zshrc, which would result in generating the shell completion scripts every time a shell is started:

eval "$(__MVT_IOS_COMPLETE=bash_source mvt-ios)" # Example for mvt-ios in bash

However, this does not work properly for MVT in a virtual env, as the mvt commands are only available once the env is activated, not upon opening the shell. It would then result in an error:

bash: mvt-ios: command not found

We could consider adding the eval instructions for users who installed MVT system-wide.

[nimrod-a]

@besendorf and I discussed that it may make more sense to source the command completion files automatically. New users benefit from command completion the most, so it would be more useful if the user would not need extra steps for activating it.
Any idea how we could run the following automatically in pip/docker post-install?

 . .mvt-android-complete.bash && . .mvt-ios-complete.bash # bash 
 . .mvt-android-complete.zsh && . .mvt-ios-complete.zsh # zsh