[WicketDemo-develop] source update: unit tests added (more)

[WicketDemo D. C. <wic...@li...>]

Cranked up the test coverage to 66%, most packages are now covered
satisfyingly.

-> Packages that are ok:
net.sf.wicketdemo.app.errorhandling
net.sf.wicketdemo.app.themes
net.sf.wicketdemo.app.wicketpages.lists
net.sf.wicketdemo.common
net.sf.wicketdemo.common.page
net.sf.wicketdemo.domain
net.sf.wicketdemo.service
net.sf.wicketdemo.tech
net.sf.wicketdemo.tech.domain
net.sf.wicketdemo.tech.service

-> Packages that can be improved (not urgent, can be left alone for now):
net.sf.wicketdemo.app.links
net.sf.wicketdemo.app.menuandtree
net.sf.wicketdemo.app.wicketpages
net.sf.wicketdemo.app.wicketpages.component