Adding sxp features

Adding sxp features

1) Feature Tests Pass: https://jenkins.opendaylight.org/releng/view/sxp/job/sxp-merge-stable-lithium/org.opendaylight.sxp$features/6/testReport/
2) Features Comply with Guidelines: https://git.opendaylight.org/gerrit/gitweb?p=sxp.git;a=blob;f=features/src/main/resources/features.xml;
	a) Feature Names (prefixed with 'odl-'): odl-sxp-controller
	b) Features Descriptions: Present
	c) Features Start-Levels: No start-levels on <bundle> elements or <feature> elements
3) Features Tested: Features have been tested for functionality with
	a) feature:install odl-sxp-controller
	b) feature:install odl-sxp-controller, odl-integration-compatible-with-all
4) Integration Test Impact: none

Signed-off-by: Martin Sunal <msunal@cisco.com>