Add translations test

Add a new test suite to verify the correct usage of the t() functions.

For instance:
t2('%s test', '%d tests', 1);
is wrong, since gettext can't compile the .po file (for the above example
msgfmt exits with the error message
"format specifications in 'msgid_plural' and 'msgstr[0]' for argument 1
are not the same")
Remove useless line
Fix greedies regex when Content Helper import function replace multiple links in the same line
Merge pull request #1796 from mlocati/add-translations-tests

Add translations tests
Fix output of localization test messages
Merge pull request #1798 from mlocati/fix-localization-test-error-messages

Fix output of localization test messages
Fix greedies regex with a more read friendly syntax
Merge pull request #1799 from nebuleu/fix-content-helper-import-regex

Fix regex when Content Helper import() replace multiple links in the same line
Encoding themeHandle variables in order to prevent XSS vulnerability.
changes htmlentities to concrete5 h function. Thanks mlocati.
Merge pull request #1801 from mmetince/master

Encoding themeHandle variables in order to prevent XSS vulnerability.