Update theme links on forum, textpattern.com and wiki page to consistent wording and useful target

[jools-r]

Just acting on Peter’s request on the forum:

• The External Textpattern Links section on textpattern.com (left col at the bottom) is called “Templates” rather than “Themes” and links to a currently empty site at http://themes.textpattern.com/.
• The “Themes” link on the forum main nav points to the “Creating Textpattern Themes" page (see next bullet point) not to a source of themes.
• On the wiki page on creating themes the "Themes" link in the main nav at the top points to the now defunct textgarden.org.

Suggestion: perhaps themes.textpattern.com is a good destination and just needs some interim links to actual sites with theme links until a new site is up. See Peter’s forum post for a start.

[1zero]

Suggestion: just point all themes links to txpthemes.com where there are working themes.

[rwetzlmayr]

I've established a web server at http://themes.textpattern.com/. Redirection target could be the subject of some further discussion if anyone wants to.