Makes progress on #4

* PATV/README.md:
* SO/README.md:
  - Compatibility: Reword for clarity
  - Use: Reword for clarity
  - See also: Add issue tracker,
    roadmap, license, subsection
	headings and link icons

* PATV/promo/README-moddrop.md:
* PATV/promo/README-nexus.bbcode:
* SO/promo/README-moddrop.md:
* SO/promo/README-nexus.bbcode:
  - Propagate changes from READMEs
  - Fixes to display on the sites

* PATV/promo/icon-moddrop.png:
* SO/promo/icon-moddrop.png:
  - Add enlarged icons that display
    better on ModDrop.