CLOUDSTACK-8011: Upgrade maven dependencies

Changes;
- Upgrades maven-war plugin to 4.5 (faster war packaging)
- Upgrade spring framework to latest minor release
- Upgrade ehcache, jasypt, httpclient, httpcore and other core dependencies
- Upgrade to latest ipv6 library, fix unit test NetUtilsTest
- httpcore and httpclient are sharing same version variable
- commons-httpclient is different that httpclient, the fix gives it a separate var
- Apidocs failed to generate and get stuck with new reflections version, for now
  we will continue using 0.9.8

Newer dependencies can be listed using:
mvn versions:display-dependency-updates -Dnoredist -Dsimulator -P developer,systemvm

Testing;
- Tested using Maven 3.2.1
- Local noredist build with unit tests succeeds
- CloudStack mgmt server started, basic business layer tests work
- Observed 10-15% build time improvement using new maven-war plugin

Branch: bugfix/4.5-8011 (commits are squashed in favour of a linear history)

Pull request:
https://github.com/apache/cloudstack/pull/50

This closes #50

TravisCI build summary:
https://travis-ci.org/shapeblue/cloudstack/builds/42902172

- Build passes with unit tests
- Apidocs generates successfully
- Most integration tests pass, some fail due to timeout errors, second re-run
  passes some of them

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>