De-emphasize manual game add

[jazzsequence]

There are very few cases where it would be desirable to manually add a game rather than use the BGG add.

Description
As a user, I want a single "Add Game" link rather than multiple links that (appear to) do the same thing.

AC

• Add New from BGG is considered the "default" workflow
• Add New is de-emphasized (all Add New links point to Add New from BGG?)
• Remove Add New from menu?
• Add an "Add game manually" to the "Add New from BGG" page
• Rename "Add New from BGG" to just "Add New" and emphasize that this plugin integrates tightly with BGG's database by default
• Update documentation