Issue #430: Removing $page_top variable.
Merge pull request #580 from dougvann/issue-430

Issue #430: Removing $page_top variable.
Issue #193: Flatten classes in templates using implode().
Issue #193: Flatten attributes in templates using backdrop_attributes().
Issue #193: Remove title_attributes everywhere except for the dynamic block.
Issue #193: Flatten content attributes in templates using backdrop_attributes().
Issue #193: Flatten html, body, and item attributes in templates using backdrop_attributes().
Issue #193: Rework color module to use hook_css_alter().
Issue #193: Retrieve html head, css, and js directly from page templates.
Issue #193: Rework code from template_process_username() into theme_username().
Issue #193: Move views process function code into preprocess, and clean up classes.
Issue #193: Move contextual process function code into preprocess.
Issue #193: Move layout process function code into preprocess.
Issue #193: Remove the process phase of the theme system.