Provide shell command completion support (for Bash)

[PatrickLehnerXI]

Most shells offer tab completion to automatically complete commands and arguments based on what the user has entered on the prompt so far.

These completions usually automatically include things like all executables on the PATH, or local files and directories.
Additionally, they can usually be extended by users and third-party programs, e.g. to add (more or less intelligent) completion of sub-commands and command-line options of programs. A popular example is Git, which offers brings tab-completion for the Bash shell, with which you can complete Git sub-commands, branch names, etc.

It would be a great convenience feature for DevCmd to offer completion integration with popular shells, so that the locally available devcmd tasks are automatically completed.

The integration is usually shell-specific and therefore needs to be done individually; I suggest that we start with Bash, since this is still a very popular shell.

The tab-completion for devcmd can probably make good use of the "list" option (#30), or a variant for machine consumption.