Support for defining ENV variables

[soebbing]

It would be nice to be able to define some ENV variable in the scripts.

e.g. this command prints out the database credentials for every one to see (and they might
even be logged). It would be great to be able to define an ENV variable to hold the password, in the case of mysql this would be MYSQL_PWD

mysql -u '__DB_USER__' -p'__DB_PASSWORD__' -h '__DB_HOST__' --port='__DB_PORT__' -e "DROP DATABASE IF EXISTS \`__DB_NAME__\`"

[JanPietrzyk]

Hey, the new XML-Syntax should enable this nicely:

<const name="MYSQL_PWD" envVar="true">test</const>

like that?