add dotdict module under dbsake.util
add pathutil under dbsake.util

- this centralizes various convenience methods for working with
  types of paths either for commands or in the filesystem
rewrite of split-mysqldump command

- split-mysqldump is now named "sieve"
- largely rewritten backend api with many new features
- updated front-end api with many new options for end users
cleanup sieve debug output
add additional debug logging when a table is filtered
remove overly chatting "discriminator" debug messages

- not very useful to an end user and only included while
  debugging parsing logic.  This should be covered by a test
  case rather than spamming a user wanting to see debug output
Merge branch 'feature/dumpsplit_to_sieve_refactoring' into develop
update README.rst examples

- update the quickstart examples to reflect changes in dbsake 2.0
sandbox/datasource.py: tables -> include_tables

- fixing breakage due to earlier api changes
sandbox/datasource.py: fix bad cmd api use

- more patterns of cmd = cmd.run(...)
- other cases fixed where a result object is expected rather
  than a simple returncode
bump documentation version to 2.0.0-dev
update subcommands for 2.0.0 release