Add license files to the nginx tarball

This PR fixes the nginx build - it was dying with
```
checking for PCRE library in /opt/local/ ... not found

./configure: error: the HTTP rewrite module requires the PCRE library.
You can either disable the module by using --without-http_rewrite_module
option, or install the PCRE library into the system, or build the PCRE library
statically from the source with nginx by using --with-pcre=<path> option.
```
and also ensures that the LICENSEs are included in the nginx tarball
```
$ tree -L 4 /app/nginx 
/app/nginx
| ...snip...
`-- share
    `-- doc
        |-- nginx
        |   |-- CHANGES
        |   |-- LICENSE
        |   `-- README
        `-- pcre
            |-- AUTHORS
            |-- ChangeLog
            |-- COPYING
            |-- html
            |-- LICENCE
            |-- NEWS
            |-- pcre-config.txt
            |-- pcregrep.txt
            |-- pcretest.txt
            |-- pcre.txt
            `-- README
```