Adding ability to pass inputs & parameters into pipeline using pom file.

I need to execute a pipeline which includes input ports & parameters.  The plugin didn't support it so I added some functionality.  Let me know what you think.

- Added 'inputs' & 'parameters' configuration variables
- Since maven configuration doesn't allow maps of maps, parameters are declared as
  a map with the value being a '<key>=<value>' string
- Inputs have their URI constructed starting from the current working directory

The resulting code accepts a maven configuration like:
```
<configuration>
    <pipeline>generateSamples.xpl</pipeline>
    <inputs>
        <source>sample_product_schemas/cloudbackupBandwidthIn.xml</source>
    </inputs>
    <parameters>
        <parameters>base_feed_name=backup</parameters>
    </parameters>
</configuration>
```