SimpleToString plugin and new features for ToString plugin

[laurentschoelens]

Based on #432, we want a SimpleToString plugin with no external runtime dependency. Based on true-experience, this plugin should support ignoring fields, masked fields and formatting fields (for date based fields)

[mrpiggi]

Not sure if this is really helpful (especially as you already started to work on this topic) but https://github.com/patrodyne/hisrc-basicjaxb/tree/master/plugins/src/main/java/org/jvnet/basicjaxb/plugin/simpletostring holds something

[laurentschoelens]

Thanks @mrpiggi The plugin already had a PR but I need rework for formatting date fields solution