openshift.sh: Add CONF_CARTRIDGES

Add the following setting, as documented in the script:

cartridges / CONF_CARTRIDGES
  Comma-separated selections from the following:
    all - all cartridges;
    standard - all cartridges, excluding JBossEWS or JBossEAP if
      CONF_NO_JBOSSEWS or CONF_NO_JBOSSEAP, respectively, is
      specified;
    cron - embedded cron support;
    diy - do-it-yourself cartridge;
    haproxy - haproxy support for scalable apps;
    jbossews - JBossEWS support;
    jobsseap - JBossEAP support;
    jboss - alias for jbossews and jbosseap;
    jenkins - Jenkins client and server for continuous integration;
    mysql - MySQL;
    nodejs - NodeJS;
    perl - mod_perl support;
    php - PHP support;
    postgresql - PostgreSQL support;
    postgres - alias for postgresql;
    python - Python support;
    ruby - Ruby Rack support running on Phusion Passenger.

  You may prepend a minus sign '-' to any one of the above to negate
  it.  For example, all,-jbossews enables all cartridges except for
  jbossews.

  Selections are parsed from left to right.  For example,
  all,-jboss,jbossews enables all cartridges except for JBoss
  cartridges, except for JBossEWS (so JBossEWS _will_ be enabled but
  JBossEAP will _not_ be enabled).  However, all,jbossews,-jboss would
  install all cartridges except for JBoss cartridges (so neither
  JBossEWS nor JBossEAP will be installed).

  Default: standard

This commit fixes bug 1055824.