Apply a default fixed font to nav-button-label when themes.googleusercontent.com is blocked from NoScript.

This maintains the nav-button height.
Libraries don't have short descriptions.. yet...
Merge pull request #86 from Martii/nav-buttonCSSsymmetry

Apply a default fixed font to nav-button-label when themes.googleusercon...
Small fix for button on ScriptEditorPage
Merge branch 'master' of github.com:OpenUserJs/OpenUserJS.org into css-alignment