Memepack-builder

Changes
* Module type `collection` updates the structure:
* Flattened the `contains` field, now only need to use an array to include all the names of wanted modules.
* The old "by type" compound is still working, but is deprecated. Planned to remove in 0.3.0.
* Error code `WARN_DEPRECATED_MODULE_TYPE` has been renamed to `WARN_DEPRECATED_MODULE_CONTENT`. The value didn't change.

Fixes
* Fixed an issue where `ModuleChecker` cannot automatically detect the classifiers of some modules.
* It's still strongly recommended to write the classifiers explicitly.
* Fixed an issue where `BEPackBuilder` use a tuple instead of string as the parameter in `_merge_language` method, therefore causing build not successful.

Module migration guides
* For all `collection` modules, update the `contains` key from `"contains": {"language": [...], "resource": [...], "mixed": [...]}` to just `"contains": [...]`.

New features
* Added `classifier` (array) to `module_manifest.json`.
* Currently only have `modified_language` and `modified_resource`.
* The `ModuleChecker` can automatically detect proper classifiers, but it's recommended to write it explicitly.

Changes
* Module types `language` and `mixed` are now deprecated. Using them will raise a warning. Planned to remove in 0.3.0.

Module migration guides
* Change module type `language` and `mixed` to `resource`.
* For modules that modified language file, add `modified_language` to `classifier` field in `module_manifest.json`.
* For modules that added resource files, add `modified_resource` to `classifier` field in `module_manifest.json`.

No changes since v0.2.0-alpha.2.

Changes
* Some internal methods changed parameter position.
* Some internal methods now supports arbitrary paramters (previously is a list). Call of these methods should now unpack the list.

Fixes
* Fixed some .py files still importing the old name, therefore causing `ImportError`.

New features
* Added `classifier` (array) to `module_manifest.json`.

Changes
* Module types `language` and `mixed` are now deprecated. Using them will raise a warning.

Module migration guides
* Change module type `language` and `mixed` to `resource`.
* For modules that modified language file, add `modified_language` to `classifier` field in `module_manifest.json`.
* For modules that added resource files, add `modified_resource` to `classifier` field in `module_manifest.json`.

Fixed the issue where `ModuleChecker` is not found.