Support system messages for upload text

[bilintsui]

Currently, the default upload text for new files is very simple, they simply just add a template using subpage name, and using additional parameters when call through parser function.

On some wikis, uploaded files need to be tagged with copyright information. which is mandatory or recommended. Currently, SimpleBatchUpload do not have the ability to set a default upload text on root page, it means editors needs to write the upload text manually, and there is usually someone forget it, increases workload for maintenance on forementioned wikis.

This PR allows administrators set default texts for root page and subpages, at MediaWiki:Simplebatchupload-filesummary and MediaWiki:Simplebatchupload-filesummary-<subpagename> respectively, the message for the root page is also registered in the message file. Additionally, optional template parameters passed through parser functions can be substituted on $1 in these system messages (prefix | included).

Some other changes are also made in this PR:

• Registered simplebatchupload-parameters system message in the message file, a message for an existing feature.
• Added support for unordered list in simplebatchupload-parameters system message, prettier in format, like the format in MediaWiki:Gadgets-definition.
• Added support for unnamed parser function call (e.g. {{#batchupload:|arg1|arg2}}).
• Added special page aliases for Chinese variants (zh-hans, zh-hant, zh-hk).

This PR should be compatible with existing usages.