Add utility conditions for language and country tags

[bgaillard]

As explained in the http://docs.pushwoosh.com/docs/createmessage documentation it is possible to specify Country and Language conditions.

For example.

"conditions": [["Country", "EQ", "BR"],["Language", "EQ", "pt"]]

It would be useful to have 2 new conditions names CountryCondition and LanguageCondition with utility constants for country codes (i.e ISO_3166-2) and language codes (i.e ISO-639-1).

Here is a sample.

CountryCondition::create()->eq(CountryCode::FR);
LanguageCondition::create()->noteq(LanguageCode::GB);

The CountryCondition and LanguageCondition classes are specific StringCondition which do not allow to specify the name of the tag.