DS-1587: Fix 1.8.x Branch for Git/GitHub

This pull request ensures the existing 1.8.x branch gets cleaned up so that it functions properly with GitHub.

This includes:
* Adding .gitattributes and .gitignore (and cleanup line endings)
* Modifying all POMs to reference GitHub instead of old SVN repo
* Merging the old "dspace-pom" functionality into the root (dspace-parent) POM, including the License header checks, etc.
* Fixes a few incorrect license headers.

(All of these changes were essentially "backported" from the 3.x branch.)

This has been tested and "mvn package" and "mvn install" (from either [dspace-src] or [dspace-src]/dspace/) now both work properly on 1.8.x.

I'll merge this PR shortly, as I believe it to be noncontroversial.  Just wanted to create this PR as a "record" of the necessary changes.

(Although this PR may look large, it mainly just updates our POMs, and most of the changes are just in terms of correcting line-endings and removal of all references to SVN)