[MCHANGELOG-127] Add ability to specify an alternate SCM connection url

**[Martin D'Aloia](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=mdaloia)** opened **[MCHANGELOG-127](https://issues.apache.org/jira/browse/MCHANGELOG-127?redirect=false)** and commented

Add possibilty to specify an alternate connection url other than the defined in the SCM section, similar to the SCM mojo of the maven-project-info-reports-plugin (see [here](http://maven.apache.org/plugins/maven-project-info-reports-plugin/scm-mojo.html#anonymousConnection)) and the ChangeLog mojo of the maven-scm-plugin (see [here](http://maven.apache.org/scm/maven-scm-plugin/changelog-mojo.html#connectionUrl))

This makes possible to generate, for example, a general site module (on a multi-module project) with general information. This is the same intention of the General SCM Project Information Report (see [here](http://maven.apache.org/plugins/maven-project-info-reports-plugin/examples/scm-report.html))

The patch provided contains one possible solution and the modification of the testcases affected by this change.
By default the 2 new parameters gets the value specified on **project.scm.connection** and **project.scm.developerConnection**

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**Affects:** 2.2, 2.3

**Attachments:**
- [custom-scm-connection-url.patch](https://issues.apache.org/jira/secure/attachment/12714472/custom-scm-connection-url.patch) (_10.47 kB_)

Start by reviewing the attached custom-scm-connection-url.patch and the test cases it modifies, then compare the requested parameters with the referenced Maven SCM mojo behavior. Done means the alternate connection URLs can be specified while defaulting to project.scm.connection and project.scm.developerConnection, with the affected tests passing.

Written by the indexing model from the issue text.