Change format of the configuration

We need to make configuration simple to read and change.
Initially the configuration file was a shell script which defined set of shell variables:
var1="tpcc_warehouses"
var1_range="100"

var2="tpcc_connections"
var2_range="1,4,8,16,32,64"
var2_iterations="3"
var2_restart_mysqld="NO"

There are some drawback of such approach\
1. Not convenient.
Users may prefer something like:
<var tpcc_warehouses>
range=100
</var>

<var tpcc_connections>
range="1,4,8,16,32,64"
iterations="3"
restart_mysqld="NO"
</var>

2. Not flexible.
In general it is hard to parse values like
mysqld_args=""--innodb_buffer_pool=3G,--user=root,--slow_log_verbosity=\"query_plan,innodb\"""