graph: added more tests

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
graph: added tests for graph_sort_successors function

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
plugins: added PluginInfoBuilder class

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
plugins: use PluginDependencyGraph as wrapper for Graph generic

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
plugins: change API of PluginDependencyGraphBuilder

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
plugins: use PluginInfoBuilder in test code

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
misc: better test for graph_sort_successors

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
misc: added move constructor to Graph class

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
plugins: add more methods to PluginDependencyGraph

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
plugins: add tests for PluginDependencyGraph

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>