helper function 'or' and 'but' rule
merge and-rule
name correction
Implementing surprisingness evaluation - half way.
Finished surprisingness evaluation.
Removed normalization for surprisingness.
Added variable number to pattern.
Consider the variable number of a pattern, when two patterns have same surprisingness value, the pattern has less variables ranks higher.
Merge pull request #1022 from shujingke/PM

Surprisingness evaluation for interesting pattern mining.
Debugging for removing the locks in calling pattern matcher.
Guile unit test: put the sequence of tests into order.
atomspace: fix broken operator<<()
scheme: Fix output port drain
Guile: provide documentation for the new code.
Merge pull request #1024 from linas/bugfix

Bugfix for #1023
Merge branch 'master' of http://github.com/opencog/opencog into PM
Removed a lock , raised the speed of mining
Possible race fix for bug #1025
Add a sanity check for multi-atom-table atom removal.
atomspace: clone atoms that belong to other atomspaces.