Revise exported CMake config

[dg0yt]

While testing 1.7.1 RC1, I found these issues with the exported cmake config:

• It uses some @PROJECT_NAME@_USE_STATIC_LIBS and the BUILD_SHARED_LIBS value when the config is consumed, but the available linkage is determined at build time.
• @PROJECT_NAME@_SHARED_LIBRARIES and @PROJECT_NAME@_STATIC_LIBRARIES shouldn't be advertised IMO. Linkage is determined at build time. The variables are either empty or libgeotiff.
• For static linkage, the config must care for the dependencies expressed in targets.
• The config was verbose even when the user passes QUIET to find_package.

This is adressed in PR, but not yet tested thoroughly.

Other isssue which are not adressed:

• If there is a desire for @PROJECT_NAME@_USE_STATIC_LIBS, a non-matching config should do nothing, giving other configs the chance to be considered by CMake.

[rouault]

Do you believe this should go in 1.7.1 (I don't want to do too many RCs...) or can this go to a 1.7.2 with further changes ? (to be honest I hardly understand those parts of cmake stuff so I'm a bit nervous to have that as last minute changes)

[dg0yt]

Well, the pristine CMake config is incomplete for some static configurations. And there is another patch in vcpkg which I would like to upstream. OTOH it is not yet ready, and if nobody else uses these configurations ...

In vcpkg, liblas and pdal seem to detect the bugs in this config.