Remove "HEAD" as default value for org.apache.maven.model.Scm.tag

svn log -r178317
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r178317 | evenisse | 2005-05-25 01:24:30 +0200 (Mi, 25 Mai 2005) | 1 line
Add tag to scm part

Since the very beginning the default value of the tag-field is "HEAD"
This is a typical CVS-value, which causes some trouble.
For instance almost every ScmTranslator does a check if the value of the tag is "HEAD".

This looks like a design flaw.

The proposal is to remove this value (or change it to an empty String to prevent possible NPE's). We'll probably have to check the impact for especially the CvsScmProvider.