Merge branch 'release/0.8'
Merge branch 'develop' of https://github.com/tuttleofx/TuttleOFX into dev_Host
Graph: add clear function

The function deletes all nodes and all connections from the current
graph.
Graph: fix deleteNode

Find on the map of nodes returns an iterator to the searched node if
found, otherwise it returns an iterator to map::end.
Merge pull request #344 from cchampet/dev_Host

Host Graph: clear function