PostTitle Widget: font and gradient

Open the PostTitle Widget (dashPostSubtitle) to change the subtitle font family and font color.
This widget also overrides the background-color set by the Heading Colors Widget. Since <h2> is the most frequently used heading, I thought it might be nice to give users even more control over it.
If you set the $Color of this widget to #fff, then it is ignored and the <h2> from the Colors Widget is used. But if you set the $Color to anything else, this value will override. The bonus feature here is that you can also set $Color2, which makes your <h2> export as a two-tone fade-out gradient—from $Color to $Color2 (at 100% transparency).
The value of $OpacityRight determines the transparency of the right-hand side of all heading background colors. For all headings, this will be a left-to-right fade from $Color to that same color. For <h2> only, if $Color of dashPostTitle is not #fff, this will be a fade to $Color2.
