Fix use of the cmake package (#146)
Fix use of the cmake package (#146)

Fix use of the cmake package

Fix use of the cmake package and its imported targets.
Make sure that the include dir comes with the cmake targets
Put everything under md4cConfig so that the md4c-html can see
md4c.
Use md4c namespace so that the targets become md4c::md4c and
md4c::md4c-html following cmake standards for imported targets.

Fixes #145.
mity/md4c,mity/md4c,mity/md4c