Blocks app bug fix

Blockgroup action returns FALSE if not blocks are assigned
Blocks app API bug fix

Removed reference to gid field in instances table (gid removed from
schema)
Blocks app bug fix

Added check to ensure blocks are assigned before displaying them in the
template. This is actually made obsolete by a previously committed fix,
but I'm leaving it for a sanity check.
Vision theme page template enhancement

Left column doesnt display as empty if no blocks are assigned to the
left blocks group.
Application Component object enhancement

Application actions can now return FALSE, which stops the object
processing and provides a way to check for output before attempting to
load a template from the action call.