1. Each sub-project must export its own configuration.

2. When building as sub-projects within SALOME GUI top-level project,
   targets file can be directly included from the GUI main configuration.
   Or, alternatively, find_package(sub-project) must be called from
   GUI main configuration file, similarly to other pre-requisites.

3. As soon as (1) and (2) are done, refactor sub-projects to:
   * Include other sub-projects recursively, following this approach,
     for example, SalomeGUI -> PyConsole -> PyInterp.
   * CurvePlot should become independent project, probably depending
     on PyInterp. Also, it seems reasonable to avoid this direct
     dependency as it is minimal de facto and needed features can be
     achieved by simple copy-paste.
   * Due to this refactoring, direct inclusion of PyInterp to PyConsole
     via add_subdirectory() will be not needed anymore.

4. Export targets for RemoteFileBrowser.