Add Grails wrapper.
Added single page webapp examples
Added nosql examples for ch17
Added dumbster for mail testing with sample integration test
Added migrations samples
Use loginId field name for search form.
Add print statements on startup.

These extra lines in the console output highlight the order in which the sample
data is loaded. In particular, the environment specific stuff appears to happen
after everything else, even though it's declared earlier.
Add chapter 18 source code.
Add chapters 19 and 20.
Renumber chapter folders to sync with book.
Remove unused files.
Upgrade QOTD to Grails 2.3.4.
Ported old Junit test to Spock
Removed old JUnit tests.
Fix indents and sync with chapter content.
Sync ch02 source with ch01.
Sync with ch03 manuscript.
Sync ch04 source with ch03 source.
Update templates for Grails 2.3.4.
Enable the custom validation error messages for ch04.