Added three functions to gbtheme to fix #17

1. `gbtheme_is_translated_node($node)` - this function will return `true` if the node's body is available in current UI language or one of the fallback languages. Otherwise will return `false`.
2. `gbtheme_is_translated_term($term)` - this function will return `true` if the temr's name is available in current UI language or one of the fallback languages. Otherwise will return `false`.
3. `gbtheme_is_translated_field($entity, $field)` - this function will return `true` if the specified entity's field is available in current UI language or one of the fallback languages. Otherwise will return `false`. You can use this to check any field for node (not just body).

You can combine this functions to achieve the result you wanted. For example:
```PHP
$node = node_load(1);
$term = taxonomy_term_load(33);
if (gbtheme_is_translated_node($node) && gbtheme_is_translated_term($term))
  print 'Something';
```

If you want to check only current UI language, then add additional parameter like this:
```PHP
$node = node_load(1);
$term = taxonomy_term_load(33);
// Adding 'false' will check only current UI language.
if (gbtheme_is_translated_node($node, false) && gbtheme_is_translated_term($term, false))
  print 'Something';
```