Used Properties to update the preferences file

This allows merging of existing preference data with downloaded data
Corrected mapping-metadata

There is no need for the plugin artifact information
Converted to trajano project

The groupId is net.trajano.mojo as this is a mojo.

The artifactId has changed to conform to Maven guidelines in that plugins
must end with -maven-plugin and not start with maven- which is reserved
for official Maven plugins.
Fix deprecated warning

[WARNING]   The syntax
[WARNING]     @parameter expression="${property}"
[WARNING]   is deprecated, please use
[WARNING]     @parameter property="property"
[WARNING]   instead.