Add support for some non-ISO-639-1 languages we support

[ngaruko]

ATM we are using this iso-639-1 library to check for language codes. Recently, we have added a few languages that are not in that standards: ceb, hil and probably tl, for ICM Philippines. So, when one runs the upload-custom-languages command in medic-conf CLI, an error is thrown I wonder if there is no package for ISO-639-2. Maybe iso-639-2-english - that way, we will have covered quite a good range of languages, just in case.

[mrsarm]

@ngaruko The primary problem here is that the message is shown with ERROR verbosity instead of WARN in medic-conf, making unclear for the user at first sight whether the process was aborted and the language was uploaded or not, which is not the case: the language is uploaded and the process not aborted.

What we need to do is:

• When a language is not recognized change the verbosity of the message from ERROR to WARN as it was previous to release 3.4.0 of medic-conf (not a change in this library).
• Check whether we can use an ISO-639-2 package from Npm to recognize the language codes.
• Add ceb and hil as possible non ISO languages to the exception list if the new ISO library doesn't include them (tl is currently supported by the ISO library used).
• Also add the ability to receive a list of possible non ISO codes to the exceptions list, so new languages we want to support in the future don't require a new release of the library to avoid the warning message.