begin transition from English to ISO-639 with #234

This patch converts all English language strings used within
depressionbot's localisation interface (that is, strings.json) to their
ISO-639-1 equivalents.

The purpose of this patch is to make the strings.json file less
English-dependent.

All languages with an ISO-639-1 code have been converted; that is,
English, Spanish and Welsh, to ``en``, ``es`` and ``cy`` respectively.

This patch does not attempt to force a solution to the issue of Na'vi:
the language does not have a large enough corpus to warrant its own ISO
639-3 code, and as such there is no perfect solution. For the time
being, this patch keeps the Na'vi language as its English language
string ("Na'vi"). A possible solution to this discrepancy includes using
the ISO 639-3 code ``art``, used for artificial languages that do not
qualify for an official code, or by using local use codes specified
in ISO 639-3 (qaa to qtz).

This patch requires collaboration with upstream repositories that also
use strings.json, such as the Github and Stats modules.
Merge pull request #275 from tmenari/master

my spotify module
Merge pull request #277 from tmenari/master

fix spotify search crash
Merge pull request #278 from tmenari/master

[spotify] show title when searching
convert hyphens to a more appropriate en-dash
fix dash
Merge pull request #279 from zuzak/dash

convert hyphens to a more appropriate en-dash
Merge pull request #274 from zuzak/langs

begin transition from English to ISO-639
Convert core strings.json to ISO 631
Merge pull request #280 from zuzak/patch-3

Convert core strings.json to ISO 631
~link to use event input not params [Fix #273]
Merge pull request #285 from SamStudio8/master

~link to use event input not params [Fix #273]
Fix [#286]
change default lang to en so no crash
dont bother with titles if they are too long
add basic, hackish finger functionality
add string functionality
add hackish handling of non-existent users
Merge pull request #301 from zuzak/finger

Finger: #297
entity decoding for link module