Avoid Database::tableName in WikiExporter

Avoid Database::tableName in WikiExporter

Using * in select is not the prefered way.
List all needed columns to make the use visible and to avoid issues when
new fields gets added with big data.
As each column name is unique there is no need to get the table name for
prefixing the columns

The following columns no longer selected:
- log_user_text -> not used due to use of ActorMigration class
- log_actor -> Add by ActorMigration class
- log_comment_id -> Added by CommentStore
- log_page -> Unused in the writer, the ns/title pair is used instead

Move the arrays out of the loop, because there are not depending on
values changing in the loop

Change-Id: I140641b7ed75bc2b8db2e7612020d668f1be663b