Add numeric validator for float fields by default.

Make bake add numeric validator to float fields.

Fixes #2163
Deprecate features being removed in 3.0
Correct 'an URL' to 'a URL' in docblocks
Merge pull request #2175 from bcrowe/hotfix-aURL

Correct 'an URL' to 'a URL' in docblocks
Makes DboSource less string dependent.
Merge pull request #2178 from Phally/master-dbosource

Makes DboSource less string dependent.
Update version number to 2.4.2
Strict null check on group parameter
Sync skel and app directories.

Closes #1698
Add space between classname(s)
Merge pull request #2180 from bcrowe/hotfix-strict

Strict null check on group parameter
Merge pull request #2181 from bcrowe/hotfix-classname

Add space between classname(s)
Renamed $sortby to $sortBy in sortByKey
Fix delivery issues with long subject lines and MailTransport.

A few people have reported issues sending wrapped messages via
MailTransport. Removing the new lines has been suggested as a fix.

Refs #2176
Merge pull request #2184 from ravage84/sortby

Renamed $sortby to $sortBy in sortByKey
Optimize _clearCache().
It is cheaper to make an assignment or call strtolower() than to pluralize.
Merge pull request #2186 from bar/clearcache

Optimize _clearCache().
Revised CakePHP and external links on the home page
Some DocBlock improvements for Model.php
Merge pull request #2188 from ravage84/model-docblocks

Some DocBlock improvements for Model.php