remove custom error handling

removes information from traceback when exception is raised
add field types and validators to premacop namespace
split decoding from model mapping in formatter

premacop already does the decoding
fix minor code styling issues
add content-type when sending PUT or POST requests in tests
clean up cruft in device tests

remove redundant code and make tests a bit more clear to read
add premacop parser to device resource
add premacop parser to extension resource
remove cruft from line_extension tests
add premacop document parser to line_extension resource
add premacop parser to line_extension_collection resource
remove fields that were never used
PAINFULLY remove cruft from tests in line resource
add premacop parser to line resource
add premacop parser to user_cti_profile resource
clean and rewrite user_line tests
add premacop parser to user_line resource
add premacop parser to user resource
remove cruft from user_voicemail tests
add premacop parser to user_voicemail resource