Ignore built files (from strukt ?)
Add a new string allocation function: join_string_sep(a, b, c)
Concatenate a and b with sep in between, if a is not empty.
If a is empty, return b.
Implements HTTP CORS (http://www.w3.org/TR/cors/).
See also flowchart diagram here: http://www.html5rocks.com/static/images/cors_server_flowchart.png

Implementation is in rest_process_cors, called after rest_ll_process_request.
Add OPTIONS command handling.

Add 2 callbacks in rest_interface:
- options: a default implementation is provided in the rest layer, if not specified in the above layer
  interface
- allowed_headers: is called to set Access-Control-Request-Header header value

TODO:
- check request headers validity for preflight requests
Add Access-Control-Max-Age with default value of 24hr
Update gitignore
Allow to parse Accept header like the following (done by jquery ajax request):
   Accept: application/json, text/javascript, */*; q=0.01
Merge branch 'master' into cors3

Conflicts:
	corest/rest.h
Merge pull request #25 from jeanparpaillon/cors3

Cors3