blade-build

Blade 2.0 release. Fixed some bugs and update some docs based on V2.0-pre2.

• protoc supports multiple plugins (#943)
• Fix py3 popen encoding issue (#938)
• Fix mac compatible issue (#937)
• ...

Add more bugfix on beta1
Support re and open to DSL

Include some bugfix. Already ran in internal environment for 2 days

This is the v 2.0 beta version. Verified in the internal production environment.

Features:

• Inclusion check for "hdrs" and private headers
• The new "load" statement to write and use extension
• Visibility is private for all targets by default and supports "legacy public" to fit the old codebase.
• A better method for append/prepend config items
• Concurrency maven downloading
• Many performance improvements, code quality improvements include refactoring, ci, testing, docs, lint, and bugfix

Include many new features and improvements! See Upgrade Notes for details.

This is the last version before 2.0, merged all trivial bugfixes and changes.
In the developing version 2.0, we will provide full functional java/python support, and support ninja as a backend, which makes building speedup tremendously!