Make usercreatepolicy pass DelegateAccount

Fixes TOOLS-274
Implement DescribeInstanceAttribute

Fixes TOOLS-102
TOOLS-282
switched to look at account alias
TOOLS-184
ensure files identified as kernel or ramdisk don't get re-registered as image
Merge branch 'master' into requestbuilder

Conflicts:
	euca2ools/commands/euare/adduserpolicy.py
Port DescribeInstanceAttribute to requestbuilder
Version bump (3.0.0 alpha 5)