First version of do-files
Install all ado-files from a specified directory

Used at New Hampshire 2014 training.
Bug fix

This seemed to affect mostly only Mac users.
Clean exit if there are no ado-files

Previously this resulted in an error on some machines, I think due to
how the braces of the Mata block were parsed.
Trim white space
Remove overzealous check of embedded double quotes
Remove -set more off-
Install specific ado-file or all ado-files of a directory
Style tweaks
Create the system directory before the loop
Merge branch 'install-dir'
Remove authors and date of last revision
Remove the `cmdname' parameter
Prepare to install multiple source code file types (not just ado)

The do-file now also installs help files without ado-files, e.g., for
the SSC package -fastcd-.
Warn when installing help files only
Update list of extensions to install