Create repository shadow using command line args.

The date of the first commit for the new repository will be overridden by the date of the reference repository's first commit (not yet implemented). Expanded the help text to specify how to add extra parameters to the 'fossil init' command that will be called.
Use proper format for datetime.

The placeholder for reference repository's first commit date has the proper format now. It still needs to be actually read from the reference repository however.
Fixed help text syntax.
Added MIT license.
Remove repo_path from fossil init args.

The reference repository is not needed when issuing the command 'fossil init'.
Wrap 'fossil init' arguments in quotes.

The argument for --date-override requires quotes due to the existence of spaces. It's a good idea to wrap the path to the new repository in quotes too.
Added skeletons to get and set project IDs.

The functions currently contain placeholder code.
s/bare_repo_path/shadow_repo_path/g.

The term 'bare repository' may be confusing because it is different from a bare git repository.
Check the return value of system commands.

The return value of each system call is checked so that script execution stops if an error occurs at any point.