More search/filtering functionality

[awebeer256]

• Search for an "exact phrase". (Currently, searching for thisphrase returns results containing this phrase, which is also bad.)
• Exclude results that match a -keyword.
• Exclude results of specific categories (and more than one at a time).
• Exclude results whose publish/update date is older/newer than X.
• Exclude results whose weekly and/or total installs are lower/higher than Y.
• Include or exclude results with a specific licence.

I'd also like the ability to browse categories and authors, without needing to know what any of them are beforehand.