Merge pull request #216 from Mimino666/shell-spider-option

Added --spider option to "shell" command.
Merge remote-tracking branch 'upstream/master'
Added COMMAND_RUN setting to commands, which need to be hooked.
Added more detailed error message, when something fails.
Added better handling of invalid http headers.
Raise BadHttpHeaderError exception when bad header occurs.
Added option to enable/disable HttpErrorMiddleware through
'handle_httpstatus_all' setting in spider.
Fixed error message formatting.
log.err() doesn't support cool formatting and when error occured, the message was:
	"ERROR: Error processing %(item)s"
Merge branch 'http-error-handle'