tests/input/logictree_test:

Added a characteristic source to the `test_source_type` test case.
tests/input/logictree_test:

s/Testeable/Testable/g
input/logictree:

Added characteristicFault to logic tree filtering.
tests/input/logictree_test:

Updated `test_source_type` to include a characteristic source in the test
cases.
Merge pull request #1097 from larsbutler/char-source-lt-support

Characteristic source logic tree support

[r=matley] [f=*1144225]