Missing fonts and mismatching PostScript names

The following PostScript names are present in font files from the Google Fonts API (https://www.googleapis.com/webfonts/v1/webfonts), but are not present in this repo. Some are missing entirely (e.g. Changa, see #1090) and some just have mismatching PostScript names (e.g. Corben Regular has the PostScript name `Corben-Regular` in this repo and `Corben` in Google Fonts).

* Changa-Bold
* Changa-ExtraBold
* Changa-ExtraLight
* Changa-Light
* Changa-Medium
* Changa-SemiBold
* Corben
* DavidLibre-Bold
* DavidLibre-Medium
* DavidLibre-Regular
* Exo-DemiBold
* Exo-DemiBoldItalic
* Farsan-Regular
* Galada-Regular
* IndieFlower
* Kavivanar-Regular
* KumarOneOutline-Regular
* Lato-Hairline
* Lato-HairlineItalic
* Maitree
* MiriamLibre-Bold
* MiriamLibre-Regular
* SourceCodePro-Semibold
* SourceSerifPro-Semibold
* Spectral-Bold
* Spectral-BoldItalic
* Spectral-ExtraBold
* Spectral-ExtraBoldItalic
* Spectral-ExtraLight
* Spectral-ExtraLightItalic
* Spectral-Italic
* Spectral-Light
* Spectral-LightItalic
* Spectral-Medium
* Spectral-MediumItalic
* Spectral-Regular
* Spectral-SemiBold
* Spectral-SemiBoldItalic

It also seems like PostScript names for individual fonts have changed over time. For example, the PostScript name for Ubuntu Regular is now `Ubuntu-Regular`, but it used to be just `Ubuntu`. Many applications use the PostScript name to uniquely identify fonts so changing it is problematic. Please consider keeping them constant to minimize disruption.