debian/control: adding dependencie on icedove-dev and python-ply

phyton-ply should be already be depended by icedove-dev.
create possibility for rebuilding 'sogo-connector.xpt'

Adding a separate makefile in 'components/' so we can clean up the
original shipped *.xpt files and recreated them.
debian/rules: force rebuild of the sogo-connector.xpt file
debian/control: add build-dependecy

Now that we use a separate makefile for rebuilding the file
sogo-connector.xpt we have to add a build dependecy for make.
document changes and release 17.0.6-1