Added Valgrind to docker file.
Split Pattern Miner into Breadth First mode and Depth First mode.
Implemented the schedule process of Depth first mining algorithm.
Commit before switch branch - on the way of implementing Depth First mining.
Merge branch 'master' of http://github.com/opencog/opencog into PM
Added new parameters to pattern miner config file.
Implemented extracting n-distance neighbour links.
Scheduling frequency and interestingness evaluation for Depth First mining.
Added filters to depth-first pattern growing algorithm. All links should be connected by variables not const nodes; All leaves should not be variables.
Added customerized filters for growing patten.
Added options of filters in config file.
Added more debug output
Made default mode in example config file as Breadth-first
Merge pull request #1043 from shujingke/PM

Finished Depth first incremental mining implementation.