Bug fixes

fixed error in image_import_zip.install
cleaned code using coder module

Backport of fixes from Drupal 6 version: Uses API to fetch remote files, fixes minutes-to-seconds conversion in cache.

Fixes "Star Trek: The Search for Spock" bug. Minutes value for cache wasn't being converted into seconds.

#138860 by bwynants - Performance tweaks.. and moved "masquerade as.." under new heading.
#174650 - access denied when attempting to switch back
#227924 - integration with alt_login
#268487 - add a database cleanup cron when people don't use the switch back link

Misc bugfixes

#280874 : DHTML Menu private functions aren't always available. Using theme() instead.