Initial commit of code for MediaWiki core.

[add] MediaWiki core files.
Subtree merged in Cite extension repo
Subtree merged in ConfirmEdit extension repo - branch REL1_21
Merge pull request #1 from jtrein/WELCOME

Initial commit of code for MediaWiki core. (note: self-merge by jtrein)
Merge pull request #2 from jtrein/Task/ext-cite-subtree-merge

Subtree merged in Cite extension repo (note: self-merge, jtrein)
Merge pull request #4 from jtrein/Task/ext-confirmedit-subtree-merge

Subtree merged in ConfirmEdit extension repo - branch REL1_21 (note: self-merge, jtrein)