Improve Bootstrap 'Quick Start' help output and/or documentation

Start by running curl bootstrap.f0cal.com/master | python3 - --help and inspect the bootstrap script's help output and the post-install f0cal/README.md instructions. Compare the current output with the requested introduction, usage example, option descriptions, and next steps; the work is done when a first-time user can understand what bootstrap installs, how to run it, and what to do afterward.

The 'Quick Start' experience is a bit cryptic. Among the documentation, the help message, and the code, none clarifies what this is doing, what to expect, or what to do next.

As-run:

curl bootstrap.f0cal.com/master | python3 - --help

Problems:

• There is not a clear division between the download and the help content.
• It is not clear what application or workflow this help is for.
• It is not obvious what the bootstrap is supposed to accomplish when run without --help.
• It is not obvious how to run bootstrap without the --help option.
• It is not clear what to do after the bootstrap install, such as how to start the f0cal CLI.

Suggested changes (for --help):

• Add a header, including leading whitespace to separate it from the curl download output.
• Add an introduction. Explain that this is the f0cal bootstrap script to set up f0cal tools on the local computer. Explain that when run without the --help option, it will install the f0cal tools within a new directory f0cal within the current directory, (actions related to new or existing virtual environment, or lack thereof, TBD... see other issues), then install system packages.
• Add a usage example.

For example:

(whitespace)

********************
* Welcome to f0cal *
********************

When run without the --help flag, this bootstrap script will perform the following actions:

1. Download and install f0cal tools within a new directory ./f0cal/.

2. (actions related to new or existing virtual environment, or lack thereof)

3. Install system packages such as compilers, unless run with --skip-system-packages.

Usage: 
  - [-h] [-d] [-v VENV_DIR] [--no-sudo] [--skip-system-packages] {git,local,pip}

  positional arguments:
  {git,local,pip}
    git                 Install from GitHub
  
  optional arguments:
  -h, --help            Show this help message and exit
  -d, --debug           Enable debug logging
  -v VENV_DIR, --venv-dir VENV_DIR
                        Directory at which to create python virtual environment
  --no-sudo             Install without sudo
  --skip-system-packages
                        Do not install system wide packages such as compilers

Usage example:

curl bootstrap.f0cal.com/master | python3 - -v f0cal/venv git
# Install from GitHub, using a new virtual environment for python packages, and include system wide packages.

After bootstrap installation, continue with instructions in f0cal/README.md.