* make slate v0 the default for regular sends
* add block_header_version to slate
* update doc tests for latest grin version
* rustfmt
* HACF if HF height detected
* rustfmt
* move api deser types into separate types mod
* rustfmt
* missing types file
* make all exports from libwallet more explicit
* rustfmt
* add version check function to foreign api
* rustfmt
* change check_version return value to result, for consistency
* add slate upgrading/downgrading
* add slate versions
* slate versioning compilation and tests
* transaction slate responses downgrade themselves to the version of the caller
* add command line arg for target slate version output
* v2 versioning comment info
* doctest fixes