Split up MeanAbsolutePercentageError and MeanAbsolutePercentageErrorTest

meanabsolutepercentageerror and meanabsolutepercentageerrortest into files for each class in there
i.e., geometricmeanabsolutepercentageerror and test and
meansignedpercentageerror and test
Split up errormeasuretest.py into files for each test class
Changed result format of SMAPE from 0.1 to 10%

Consistency. All other *PercentageErrors return 10% rather than 0.1
Fixed MeanSignedErrorTest and fixed MeanSignedError

MeanSignedError calculated originalValue-calculatedValue
which is clearly the wrong way:
http://en.wikipedia.org/wiki/Mean_signed_difference
Removed unnecessary test in MeanSignedDifferenceError for Lists
Put test for BaseErrorMeasure.confidence_interval into BaseErrorMeasureTest

removed it from all other unnecessary locations
MeanAbsolutePercentageErrorTest uses the new test data set now.
Made more test use the new test data set and move tests

Moved number_of_camparison_test from MSETest to BaseErrorMeasure test,
since it's just testing one of BEMs methods. Also added a test there for
_get_error_values which tests for proper responses to wrong start and
end dates in BEM._get_error_values.
Added stuff from pycast_publications repository