Prevent table entry syntax swallowing multiple preceeding blank lines
(a) this shouldn't be necessary, blank lines are handled by paragraph
    processing
(b) avoids issues with greedy table syntax competing with plugins

http://english.stackexchange.com/questions/117552/why-does-information-not-have-a-plural-form

do not capture groups in media_isexternal. saves perhaps some cpu cycles and some bytes memory

This reverts commit 9b47ccb8.