Upgrade i18n-abide + grunt-i18n-abide (bug 1014168)

* Upgrade i18n-abide 0.0.17 -> 0.0.20
* Upgrade grunt-i18n-abide 0.0.9 -> 0.0.12
* Rename the locale dirs for subtag locales e.g. sr_LATN -> sr_Latn
* Remove srp locale as no long part of our project locales.