Try multiple configuration files for airship config and maven settings file.

If no user specific file exists, try

* /usr/local/etc/airship/airshipconfig.properties
* /etc/airship/airshipconfig.properties

This allows global installation of airship configuration instead of
requiring a per-user setup.

For asconfig, if no user specific ~/.m2/settings.xml file exists, try

* /usr/local/etc/airship/maven-settings.xml
* /etc/airship/maven-settings.xml