Use domain "tools" for translations
Remove translations for development messages
Created `tools.pot`

* used `cake i18n extract`
Removed existing `.pot` files in favor of new `tools.pot`

* affected files: `captcha.pot`, `change_password.pot`, `confirmable.pot`
Merge existing single `.po` files to one `tools.po` each language

There were single `.po` files which contained only a few translations.
Now, they have been merged with `tools.pot` containing the strings which
have already been translated, but also all the other strings of the plugin.

I used `msgmerge --no-wrap $existing tools.pot`

* German: `captcha_de.po`, `change_password_de.po` and `qlogin_de.po` have
  been concatenated and merged with `tools.pot`
* Czech and Spanish: `change_password_cz.po`/`change_password_es.po` have
  been renamed and merged with `tools.pot`
Updated README.me: translations now use `tools` domain
CaptchaHelper: Direct call of `__d()` for each number string

Because of better maintaining `tools.pot`, gettext is called directly for
each number in the array instead of passing a variable. The Cake I18n Shell
better recognizes these strings.

`tools.pot` and `{ces,deu,spa}/LC_MESSAGES/tools.po` have also been
adjusted:

* `cake i18n extract` for generating `tools.pot`
* `msgmerge --no-wrap --update --backup=off $lang/LC_MESSAGES/tools.po tools.pot`
  for each language (`cd cakephp-tools/Locale` before)
Removed more development messages from translations
Merge pull request #102 from janriokrause/master

Use one translation domain "tools"