update dependencies

This PR update Spring stack dependencies and make modelmapper an optional dependency (cf #230).

detail of updated dependencies:

* spring from 3.2.6.RELEASE to 3.2.7.RELEASE
* logback from 1.0.13 to 1.1.1
* slf4j from 1.7.5 to 1.7.6
* modelmapper from 0.6.2 to 0.6.3
* hibernate.validator from 4.3.1 to 5.0.3
* javax.validation from 1.0.0 to 1.1.0
* cglib from 2.2.2 to 3.1
* hibernate from 4.3.0 to 4.3.1 (this fixes #227)
* h2 from 1.3.174 to 1.3.175
* ehcache from 2.6.6 to 2.6.8
* async.http.client from 1.7.20 to 1.8.3
* cors.filter from 1.3.2 to 1.9
* jackson from 2.3.0 to 2.3.1

due to javax.validation and hibernate-validator upgrades, two new dependencies were added : 

* javax.el-api 3.0.0
* el-ri 1.0

maven plugins: 

* jetty-maven-plugin from 8.1.13.v20130916 to 9.1.2.v20140210
* test-jetty-servlet from 8.1.13.v20130916 to 8.1.14.v20131031
* maven-compiler-plugin from 2.5.1 to 3.1
* maven-failsafe-plugin.version from 2.12.4 to 2.16
* maven-site-plugin.version from 3.2 to 3.3
* maven-war-plugin.version from 2.3 to 2.4
* maven-javadoc-plugin.version from 2.9 to 2.9.1
* maven-deploy-plugin.version from 2.7 to 2.8.1
* maven-release-plugin.version from 2.3.2 to 2.4.2
* maven-install-plugin.version from 2.4 to 2.5.1
* maven-assembly-plugin.version from2.3  to 2.4
* maven-project-info-reports-plugin.version from 2.5.1 to 2.7
* maven-surefire-report-plugin.version from 2.12.14 to 2.16