fix x-nexe- headers bug

fix bug introduced in c776351f1461f973bda83cb8f919c982b3fbf07e
that allows user to overwrite `X-Nexe-` headers in response
Merge pull request #107 from pkit/bug_fix

fix x-nexe- headers bug
move timout setup as early as possible
implement simple job chaining

this patch adds another middleware `ChainMiddleware`
the middleware allows rescheduling of response from previous job as a new job
for the chain to work the following statements should be true:
- response should contain `X-Zerovm-Execute: 1.0` header
- response should contain `Content-Type: application/json` header, and effectively be a json job description

you can see that the application that tries to chain something should be able to set a _response header_
which means that application MUST use `message/cgi` or `message/http` as its output channel content type
ChainMiddleware MUST be placed anywhere before ProxyQueryMiddleware in the proxy-server pipeline

example job description that can output a chained job is:

	[
            {
                'name': 'http',
                'exec': {'path': 'swift://a/c/chainer'},
                'devices': [
                    {
                        'name': 'stdout',
                        'content_type': 'message/http'
                    }
                ]
            }
	]

as you can see, stdout has no path - will be sent to user, and its content_type is `message/http`
Merge pull request #108 from pkit/job_chain

 implement simple job chaining
contrib: add Vagrant scripts for dev environment
Merge pull request #109 from larsbutler/vagrant

Vagrant scripts for dev environment
produce better errors in RestController

do not invoke RestController if the request url is not an object url
fixup query string in RestController such a way that is actually visible
Merge pull request #110 from pkit/minor_fixes

produce better errors in RestController