recommended for C++ libraries

Add a libgrokj2k1-doc package for the Doxygen generated API docs, this
has been inspired from some messages in the logs about non installed
files, e.g.:

dh_missing: warning: usr/share/doc/GROK/html/index.html exists in debian/tmp but is not installed to anywhere

Add the missing Build-Depends-Package field to
debian/libgrokj2k1.symbols as suggested by lintian:

I: libgrokj2k1: symbols-file-missing-build-depends-package-field

This is just to fix some noise when running `duck` and make it easier to
find out more useful fixes in the future.

This fixes the following notices from `duck`:

I: debian/copyright:954: URL: http://www.gnu.org/licenses/: INFORMATION (Certainty:possible)
   The web page at http://www.gnu.org/licenses/ works, but is also available via https://www.gnu.org/licenses/, please consider switching to HTTPS urls.

I: debian/copyright:933: URL: http://www.gnu.org/licenses/: INFORMATION (Certainty:possible)
   The web page at http://www.gnu.org/licenses/ works, but is also available via https://www.gnu.org/licenses/, please consider switching to HTTPS urls.

I: debian/copyright:108: URL: http://fsf.org/: INFORMATION (Certainty:possible)
   URL schema changed from HTTP to HTTPS during redirect(s): http://fsf.org -> https://www.fsf.org
   Please investigate and update the URL eventually, to avoid unneccesary redirects!

The Debian Policy states that a branch can and should specified in
Vcs-Git if the packaging bits are not in the default branch, see
https://www.debian.org/doc/debian-policy/ch-controlfields.html#version-control-system-vcs-fields