Update linter module implicit none

The linter was originally intended to ensure that implicit none was in every function and subroutine. However, for subroutines/functions in a module this is not strictly necessary so long as the module itself has implicit none declared. This commit updates the linter to be made aware of this change. Note that this does not check for the case where someone has manually defined characters which should be assumed to be implicit (e.g. implict real (a-b)).