remove quantities and create test to BigDeicmal and Double quantity
Merge pull request #27 from otaviojava/issus_26

remove quantities and create test to BigDeicmal and Double quantity
26: Remove redundant types like DoubleMeasurement 

Task-Url:
https://github.com/unitsofmeasurement/unit-impl-se/issues/issues/issue/26
add convert in add and subratc operations
26: Remove redundant types like DoubleMeasurement 

Task-Url:
https://github.com/unitsofmeasurement/unit-impl-se/issues/issues/issue/26
create a new QuantityFactory
Merge pull request #28 from otaviojava/sum_subract_convert

add convert in add and subratc operations