Possible inconsistency between addon and database dependencies

[kynikos]

Currently, extensions are checking if an opened database is compatible (database_dependency_group_N), however consider this scenario in the extension's .info file:

dependencies = extensions.foo.2
database_dependency_group_1 = extensions.foo.1

If extensions.foo is really installed with version 2, the extension is shown as enabled in the database properties, but when it checks database_dependency_group_1, it will consider the database as incompatible, with non-investigated consequences.
Of course as long as dependencies and database_dependencies are kept (manually) in sync, there aren't any problems, but this duplication should be avoided, see also #358)