(cmake): sight-project installation error due to sight version

Description

To fix the main problem, SOVERSION is no longer defined for executable targets. That simply prevents from creating these useless versioned binaries.

On top of that, several other fixes were brought:

• the version attribute of the project() CMake command is used instead of redefining a custom SIGHT_VERSION variable,
• code cleaning was done around this, notably to rename FWPROJECT_NAME into SIGHT_TARGET, which is more correct with the usage of this variable,
• dependencies computing now browses OBJECT libraries targets, like io_session_obj (fixes Tuto01Basic packaging for instance where sight_io_vtk library was missing),
• dependencies computing now handles cross-repositories dependencies (fixes some child projects packaging),
• components ordering was included in a higher-level function sight_generate_component_list() for a simpler use outside Sight.

Closes #741 (closed)

How to test it?

• Use sight in a child project with a different version. The version should now be provided with the project() CMake command.

Additional tests/tasks to run

• Packaging could be affected, since we used to define project() for each target (we thought it was useful for CPACK_INSTALL_CMAKE_PROJECTS). From preliminary tests, packages seem to be ok.