Dialyzer warnings

[UncleGrumpy]

Dialyzer emits several warnings when checking packbeam.erl and packbeam_api.erl. These warnings should be fixed and a dialyzer check added to the tests.

Output from rebar3 dialyzer:

src/packbeam.erl
Line 40 Column 1: Function create/2 has no local return
Line 48 Column 1: Function create/4 has no local return
Line 73 Column 1: Function main/1 has no local return
Line 182 Column 1: Function do_create/2 has no local return
Line 188 Column 9: The call packbeam_api:create(OutputFile::any(), InputFiles::[any()], #{'include_lines':=boolean(), 'lib':=_, 'prune':=_, 'start_module':=_}) breaks the contract (OutputPath::path(), InputPaths::[path()], Options::options()) -> 'ok' | {'error',Reason::term()}

src/packbeam_api.erl
Line 98 Column 2: Invalid type specification for function packbeam_api:create/2. The success typing is (_,_) -> none() but the spec is (OutputPath::path(),InputPaths::[path()]) -> 'ok' | {'error',Reason::term()}
Line 102 Column 1: Function create/2 has no local return
Line 103 Column 37: The call packbeam_api:create(OutputPath::any(), InputPaths::any(), #{'application_module'=>'undefined', 'include_lines'=>'true', 'lib'=>'false', 'prune'=>'false', 'start_module'=>'undefined'}) breaks the contract (OutputPath::path(), InputPaths::[path()], Options::options()) -> 'ok' | {'error',Reason::term()}
Line 159 Column 2: Invalid type specification for function packbeam_api:create/4. The success typing is (_,_,_,_) -> none() but the spec is (OutputPath::path(),InputPaths::[path()],Prune::boolean(),StartModule::module() | 'undefined') -> 'ok' | {'error',Reason::term()}
Line 166 Column 1: Function create/4 has no local return
Line 171 Column 36: The call packbeam_api:create(OutputPath::any(), InputPaths::any(), #{'application_module':='undefined', 'include_lines':='true', 'lib':='false', 'prune':=_, 'start_module':=_}) breaks the contract (OutputPath::path(), InputPaths::[path()], Options::options()) -> 'ok' | {'error',Reason::term()}
Line 197 Column 2: Invalid type specification for function packbeam_api:create/5. The success typing is (_,_,_,_,_) -> none() but the spec is (OutputPath::path(),InputPaths::[path()],ApplicationModule::module() | 'undefined',Prune::boolean(),StartModule::module() | 'undefined') -> 'ok' | {'error',Reason::term()}
Line 205 Column 1: Function create/5 has no local return
Line 212 Column 36: The call packbeam_api:create(OutputPath::any(), InputPaths::any(), #{'application_module':=_, 'include_lines':='true', 'lib':='false', 'prune':=_, 'start_module':=_}) breaks the contract (OutputPath::path(), InputPaths::[path()], Options::options()) -> 'ok' | {'error',Reason::term()}