Add bilingual support: Spanish

[astrochun]

Adding Spanish support should be straight forward. There will be some changes needed:

• On the frontend, having a sidebar to select language (English, Espanol). This will set the language as a two-letter lower-case abbreviation ("en" or "es")
• On the backend, we will need to add an optional language option (default: "en") for all functions
• We will need to have content for both "en" and "es"
• Transform table columns based on language

[astrochun]

This should wait until #53 is resolved as it will make it easier after refactoring.