bugfixes, more documentation, good enough for v0.0.1 now.

mwxml2sql:
- add missing quote at beginning of text field output
- remove namespace from title before output
- -1 for "ignore size" in sql_escape, missed this one earlier
- sql escape the username field before output
- wrote page and text table fields in the wrong order, fixed (needs
  to match the order in the create statements from MW or you have
  to add a trailing line of columns when using LOAD DATA INFILE)
- fix batch writing of revs (COMMIT after every 1000 lines)
- make revision output file use full table name in filename like
  the other output files do
- if we don't write gzipped text blobs, write CREATE TABLE statement
  which uses innodb table-based compression for the text table
- quiet compiler initialization warnings

sql2txt:
- output buffer was too short, fixed segfault
- after doing a tuple which ends the line, don't refill the
  buffer, let the line processor handle it
- clean up short option handling (mismatched short and long opts)
- convert NULL fields to \N for LOAD DATA INFILE
- docs for sql2txt in README, more timing info, rerganize docs,
  note that we tested on FreeBSD too
- fix creation of output filenames with no mw version

Change-Id: I095fb169024a243ca66bb8b9e511baae06aeb197