Clean up whitespace and space-tab-mix.

refs #209
Ensure a defined localisation environment.

See e.g. the GNU gettext documentation for more details:
http://www.gnu.org/software/gettext/manual/html_node/Locale-Environment-Variables.html

refs #209
Simplify the "sudo" usage and reduce redundancies.

refs #209, #59
Use central variables for repeating filenames.

refs #209
Remove unnecessary quotes.

refs #209
Give an explicit exit status if we didn't do anything.

And move printing of the usage help into a function.

refs #209
Add description.

refs #209
Improve description of $PHP_CLI.

refs #209, #201
Only use "sudo" in the user dir admin tool if required.

It is not necessary to use sudo for the file operations if no "SUSER" has been
set in the hrm.conf file or if the user calling the "hrm" script is already the
same that was configured in this variable. Using sudo even though the user is
already the same results in non-working commands and thus no user directories
being created.

refs #59, #173, #183, #209
Add TODOs for discussion.

refs #209
Issue warning if no "SUSER" is configured.

As discussed with Aaron and already stated in ticket #173, the
installation method without "SUSER" is deprecated and will be removed in
a future release.

refs #173, #209
minor syntax cleanup

refs #209