As a user, I can call API REST to export Cucumber Tests with a saved filter

As a user, I can call API REST to export Cucumber Tests with a saved filter.

Add the possibility to call this function http://confluence.xpand-it.com/display/XRAY/REST+API#RESTAPI-/rest/raven/1.0/export/test with a filter.

Example: /rest/raven/1.0/export/test?filter=134