Move license-maven-plugin config off the server

Previously, we stored the license configuration at:

    http://code.imagej.net/licenses

But it was a pain to keep that updated and in sync with the codebase
here. It makes more sense to use a local license resolver.

Thanks to Johannes Schindelin for the idea.
Add project.rootdir that always points to toplevel

This is a bit of a burden to maintain when projects are added or moved,
but makes it easier to point to files off the root path. Usually doing
so is a bad idea anyway, but in some cases it is nice to have access to
shared configuration, such as the files in the license folder.
Update copyrights and licenses

This was done using the commands:

    mvn license:update-project-license
    mvn license:update-file-header
Extend copyright year range to 2013

It was done with the following shell command:

    git grep -l 'Copyright (C) [0-9]\{4\} - [0-9]\{4\}' | \
    xargs sed -i '' -e \
    's/\(Copyright (C) [0-9]\{4\} - \)[0-9]\{4\}/\12013/'

The license-maven-plugin would normally do it for us. Unfortunately, it
cannot, because we have the canUpdateCopyright flag set to false, so the
update-file-header goal cannot update the copyright year range on files
with existing headers. The flag must be false because otherwise, it
would overwrite each file's copyright holders (we have a few files with
non-default copyright holders listed, which we want to preserve).

In the future, we could address the issue by contributing an enhancement
to license-maven-plugin that splits canUpdateCopyright into two parts:
canUpdateCopyrightYears and canUpdateCopyrightAuthors.