added support for cookie in RestClientTarget.

also addded a constructor to RestClienException,
taking only a string arg.
Null check for cookie in Rest Client.
Allow setting multiple cookies in RestClientTest.
Set headers in RestClientTarget.
Merge branch 'master' into sso

Conflicts:
	whois-client/src/main/java/net/ripe/db/whois/api/rest/RestClientTarget.java