Org reader: Slight cleaning of table parsing code
Org reader: Use specialized org parser state

The default pandoc ParserState is replaced with `OrgParserState`.  This
is done to simplify the introduction of new state fields required for
efficient Org parsing.
Org reader: Fix parsing of nested inlines

Text such as /*this*/ was not correctly parsed as a strong, emphasised
word.  This was due to the end-of-word recognition being to strict as it
did not accept markup chars as part of a word.  The fix involves an
additional parser state field, listing the markup chars which might be
parsed as part of a word.
Org reader: Provide more language identifier translations

Org-mode and Pandoc use different language identifiers, marking source
code as being written in a certain programming language.  This adds more
translations from identifiers as used in Org to identifiers used in
Pandoc.

The full list of identifiers used in Org and Pandoc is available through
http://orgmode.org/manual/Languages.html and `pandoc -v`, respectively.
Org reader: Support inline images