Fix "nature of source text" encoding and remove key from display

[kmcmullen]

We have decided that we will explicitly spell out the "nature of the source" text in each letter ("autograph letter signed," "typed copy unisgned," etc.). rather than use the code and then need to include the entire key.

We can probably just do a find-and-replace for the codes, and then we need to adjust the stylesheet to get rid of the key. Then we'll need to re-post all of the letters.

ccda.corr01044 and ccda.corr01182 both have the explicit classCode already encoded, as an example

[kmcmullen]

I tried to comment out the key in the "_show_bottom_metadata.html.erb" file on the dev branch, but it doesn't seem like it worked...?

[kmcmullen]

With the expert help of Bianca and Brett (the BBs), we figured out what I did wrong. The key is now removed and we have found and replaced all of the classCode text. Closing this issue.