Switch source language to English

[fletchapin]

Since English is more widely used internationally, Monroe suggested we switch the source language to that and translate into Spanish using the already working Sphinx internationalization

[CandelaLencina]

#42 Finished switching the source language/making English RST files for most of the Spanish RST files. There are still a few Spanish RST files that never got converted in the process that need to be manually made and translated into English RST files.

[fletchapin]

The translated files are sitting in doc_files but they have to be swapped for the Spanish and the .po files need to be updated to complete the switch