Configure log4j.properties location

This commit introduces Log4j config separate files for gremlin.sh and
gremlin-server.sh:

* gremlin.sh: gremlin-groovy/src/main/config/log4j-repl.properties
* gremlin-server.sh: gremlin-server/config/log4j-server.properties

Test JVMs forked by Surefire and Failsafe use the server config file
by default.  The file is controlled by a pair of properties defined in
the top-level pom:

* ${log4j.properties}
* ${log4j.properties.dir}
Exclude logback when testing neo4j-gremlin

The logback slf4j binding included by neo4j-ha conflicts with the
log4j12 binding and prevents slf4j from initializing properly.  This
commit excludes the logback dependency from getting pulled in
transitively by neo4j-ha.
Merge pull request #13 from dalaro/master

log4j properties config revamp