user_dict_upgrade: correct spelling.
Update README.md.
Update ChangeLog.
define macro RIME_VERSION in CMakeLists.txt.
rime_api: add RimeApi::get_version.
Bump version to 1.2.9.
Revert "move tree_db into legacy module."

This reverts commit 69ea51cdff6ba42591c785543f65f21029f8a485.

Conflicts:
	legacy/CMakeLists.txt
	legacy/src/CMakeLists.txt