batch generate config files by user defined env variables through template files

use python to auto generate config files by template files with different user defined env variables

initial conf structure

conf
    env
        default.config
        local.config
        test.config
        online.config
    rpc(has template file)
        config.template.ini
    supervisor(has template file)
        supervisord.template.conf
    settings(has no template file just ignore)
        a.txt
    uwsgi(has template file)
        uwsgi.template.xml

step 1:
    write template file. use ${VAR_XX} to define env variable(refer to config.template.ini)

step 2:
    write default config and specific config, assign value to env variable(make sure all variables are not "")

setp 3:
    run the script with two ways:

3.1 generate all config files
    python config_manager.py conf conf/env
    conf
        env
            default.config
            local.config
            test.config
            online.config
        rpc(has template file)
            config.local.ini(auto generate)
            config.test.ini(auto generate)
            config.online.ini(auto generate)
            config.template.ini
        supervisor(has template file)
            supervisord.local.conf(auto generate)
            supervisord.test.conf(auto generate)
            supervisord.online.conf(auto generate)
            supervisord.template.conf
        settings(has no template file just ignore)
            a.txt
        uwsgi(has template file)
            uwsgi.local.xml(auto generate)
            uwsgi.test.xml(auto generate)
            uwsgi.online.xml(auto generate)
            uwsgi.template.xml

3.2 generate specific config files
    python config_manager.py conf conf/env online

    conf
        env
            default.config
            local.config
            test.config
            online.config
        rpc(has template file)
            config.online.ini(auto generate)
            config.template.ini
        supervisor(has template file)
            supervisord.online.conf(auto generate)
            supervisord.template.conf
        settings(has no template file just ignore)
            a.txt
        uwsgi(has template file)
            uwsgi.online.xml(auto generate)
            uwsgi.template.xml