Manage CppNode and CppEdge entities on incremental parsing

[mcserep]

During incremental parsing CppNode and CppEdge entities should also be managed, deleting invalidated entries related to be deleted File and CppAstNode entries.
Note that on parse new CppNode and CppEdge entities are created not only for the parsed file, thus more thorough deletion or refactoring might be required.

[mcserep]

Solved in ccb943b and 09d2685.

Note that some warnings on incremental parsing will remain, complaining about already persisted CppNode and CppEdge entities. This issue should be automatically solved by making the domainId of the CppNode strongly typed (uint64_t instead of string) and removing directory level relations (DEPENDS and PROVIDES), which should be calculated on-demand, runtime. These alterations of the CppNode and CppEdge entities were decided on the Ericsson CodeCompass meeting on the 4th of July, but are not tightly related to the incremental parsing itself and a separate pull request should be made to the main repository.