[Refactor] Some thought to commit.
[Refactor] Remove unused code.
[Refactor] Fix bug on running test related to os.environ['LANG'] == 'id'.
Move convert_safe_layer to safe.utilities.utilities.

The function is being used in safe.utilities.impact_calculator.
[Refactor] Fix merge conflict.
Move read_file_keywords from safe_interface to safe.utilities.utilities.
Merge remote-tracking branch 'akbar/safe_refactor' into jaran
Move write_keywords_to_file from safe_interface to safe.utilities.utilities
Merge branch 'safe_refactor' of github.com:akbargumbira/inasafe into safe_refactor
[Refactor] Move safe.exceptions to safe.common.exceptions.
At last, remove safe_interface from the universe.
[Refactor] Delete disabled impact functions.
Delete safe.api.

All the modules can use directly functions from safe package.
[Refactor] Update unit test.
[Refactor] Fix merged conflict.
Standardising tests in safe.impact_functions package.

* Test package should be in the same level of the module that needs to be tested

* Delete some unused functions.
Merge conflict.
[Refactor] Add function to unload the unused impact function.
Standardising test package in safe.messaging and safe.postprocessor.
Delete safe.storage.clipping.