update of the i2prouter script based upon Tanuki's 3.5.9 script

With this check-in comes an update of our i2prouter script based upon the
script src/bin/sh.script.in from the 3.5.9 source tarball of the wrapper.

Some of the benefits of this newer version include:
- logic to determine which wrapper binary to use (32bit VS 64bit) and falling
  back to alternate "bitness." This would be most useful for portable packages.
- support for far more platforms and archs than the 3.1.1 based script (such as
  Solaris, risc, os/390, HP-UX, AIX, mips, ia64, etc.)
- support for installing I2P as a daemon in most UNIX-based environments with
  the command "i2prouter install".  The installed service can be removed with
  "i2prouter remove". With testing this option has been confirmed to work in
  OSX, Fedora, Slackware, Debian, Ubuntu, FreeBSD, and SuSE.  It does not work
  in Arch Linux (yet).