Refactored the converters: now they take a TableSet
Fixed the test for exposure population
Used "table" as a common prefix for the tables inside a tableset
Merge pull request #119 from gem/refactor-converter

Refactored the conversion library
Removed conversion/validation library (now in oq-common)
Moved the tests directory inside the package
Merge pull request #120 from gem/move-tests

Moved the tests directory inside the package
Merge remote-tracking branch 'GEM/master' into rob-oq-nrmllib