Bug 7844 - plack intranet tooling for developers

koha.psgi example and plackup.sh script to run any Koha site
intranet or opac interface under plack with optional multi-process
Starman server

  plackup.sh site-name [intranet]

site-name is used to find config /etc/koha/sites/site-name/koha-conf.xml

All configuration is specified in koha.psgi, which you are welcomed to edit
and tune according to your development needs (enable memcache, enable/disable
debugging modules for plack and so on).

For deployment of opac or intranet you would probably want to take a look
in plackup.sh and enable starman as web server (which is pre-forking server
written in perl) and put some web server in front of it to serve static web
files (e.g. ngnix, apache)

When you are happy with it, rename koha.psgi and plackup.sh it to site name
and save it for safe-keeping.

This commit message is included in patch as README.plack because it includes
useful information for people using plack for first time.

Test scenario:
1. install plack and dependencies, as documented at
   http://wiki.koha-community.org/wiki/Plack

2. start ./plackup.sh sitename i[ntranet]

3. open intranet page http://localhost:5001/ and verify that it redirects
   to http://localhost:5001/cgi-bin/koha/mainpage.pl

4. start ./plackup.sh sitename

5. open OPAC http://localhost:5000/ and verify that it redirects to
   http://localhost:5000/cgi-bin/koha/opac-main.pl

6. next step is to take a look into koha.psgi and enable additional
   debug modules, save file and reload page (plackup will reload
   code automatically)