Rails3: add number.format to ro and sk locales (#4796)

Rails3: add number.format to ro and sk locales (#4796)

Test fails on Rails 3.0.11 and Ruby 1.8.7.

<pre>
Failure:
test_number_to_human_size_for_each_language(Redmine::I18nTest)
    [test/unit/lib/redmine/i18n_test.rb:114:in `test_number_to_human_size_for_each_language'
     test/unit/lib/redmine/i18n_test.rb:112:in `each'
     test/unit/lib/redmine/i18n_test.rb:112:in `test_number_to_human_size_for_each_language']:
sk failure.
Exception raised:
TypeError(<can't convert nil into String>)
</pre>

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@8742 e93f8b46-1217-0410-a6f0-8f06a7374b81