Optimization suggestions [added 2.4]

[Kirby]

1) Index on ppgal_images.dateline
2) Cut-Off setting for latest images/random images
3) Cache announcement text (to avaoin having to load parser/smilies/bbcode)
If this is not being done, you might want to consider loading smiliecache, bbcodecache
4) Avoid modifying template cache

[Zachariah]

good ideas.
- also added index to ppgal_posts.dateline