OHT feature: Add services based languages & language pairs list

I agree.
We will defining two calls as follow:

1. Get supported languages - returns list of languages with language name and code.
2. Get supported language pairs - return list of pairs with names and codes. Note: this list can be very long (1000> items).
   Optional parameter - "expertise" - will return pairs that support the selected expertise.

This is on the roadmap for the beginning of May.

Great!

In most cases, when we request the language pair, we're interested in the language pairs for a specific source language, as we know which language we are translating from and want to check if the target language selected by the user is supported, so a source language filter would be important. That would also get the number of results down a lot.

For most translator plugins, we cache that information by source language, so that we don't have to request it again if the target language is changed in the UI, so a target language filter isn't that important for us but might make sense too for other use cases.

Providing a patch. Sorry @oyagev if you worked on this. :P

Applied the patch from #1999992: Update remote languages mappings logic and implemented getSupportedLanguagePairs() and getSupportedLanguages().

Made some cleanup in default mapping list as well. That was supposed to be done in #1961130: Supported language codes.

1. +++ b/tmgmt_oht.plugin.inc
   @@ -83,35 +76,70 @@ class TMGMTOhtPluginController extends TMGMTDefaultTranslatorPluginController {
   +      // @todo: Handle exception.
   

   same as in the other, lets just return an empty array.

2. +++ b/tmgmt_oht.plugin.inc
   @@ -83,35 +76,70 @@ class TMGMTOhtPluginController extends TMGMTDefaultTranslatorPluginController {
   +    } finally {
   +
   +      return $language_pairs;
        }
   

   finally requires PHP 5.5, don't use that in D7.

   Just put it at the end, the code will go there anyway if you catch the exception.

3. +++ b/tmgmt_oht.plugin.inc
   @@ -83,35 +76,70 @@ class TMGMTOhtPluginController extends TMGMTDefaultTranslatorPluginController {
   +    $language_pairs = $this->getSupportedLanguagePairs($translator);
   

   cal this method on $translator, then you benefit from the built-in caching there.

Fixed.

Updated the list of default languages and sorted them alphabetically. There were some languages (language codes) not supported by Drupal and I commented-out them.

Thanks, committed and pushed. Not too happy about the comment style there, but lets make progress.