Add a parent for static features

Add a parent for static features

Create a maven plugin, template-feature-plugin, which replaces
mustache-enclosed tags in feature.xml with versions from pom.xml.
We process src/main/feature/template.xml and generate a
target/feature/templated-feature.xml.

Also add template-feature-parent, a POM for static features, which
wires templated-feature.xml with karaf-plugin and SFT to form package
and validate the feature.

JIRA: ODLPARENT-235
Change-Id: I2a8e1b4114e9bb2954ede8511bd991b0fca781cd
Signed-off-by: Dominik Vrbovsky <dominik.vrbovsky@pantheon.tech>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>