Update to Plone 5 and best practices

[svx]

For including tutorial.todoapp into the docs of Plone 5, we need to update the todoapp to best practices for Plone 5

• remove grok
• follow best practices how they are mentioned on training.plone.org/5
• make sure everything is dexterity
• update its own docs

[jensens]

maybe better generate all the skeleton with bobtemplates.plone and start from there on.

[hvelarde]

please don't forget to include a note on how to test with Plone 5