Add extend-diff-ignore to debian/source/options

Cleans the build and docs folder to be able to build the package
twice without problems.

Thanks: Thomas Goirand <zigo>
Add python-ecdsa to Build-Depends

Closes: #702571
Add Python 3 support to build

Closes: #697600, #749512
Thanks: Thomas Goirand <zigo>
Clean up build environment

Remove extraneous files from debian/tests as I'm noot sure when
these were introduced exactly or why but they don't appear to be
used in anyway during the build.

Clean up doc to use html/ rather than docs/ directory

Include examples/ in doc package rather than python-paramiko now
that we have python3-paramiko as well.
Update changelog for 1.14.0-2 release