debian: remove rtslib and configshell from the build dependencies

Signed-off-by: Christophe Vu-Brugier <cvubrugier@fastmail.fm>
debian: install targetcli manpage

Fixes #42

Signed-off-by: Christophe Vu-Brugier <cvubrugier@fastmail.fm>
Merge pull request #44 from cvubrugier/master

Fix issue #42 "targetcli manpage not installed by Debian package"