Restructuring into `packages`

[tjanc]

All dependencies including drafter are now contained flat in ./packages/:

• ./packages/apib-parser/ - API Blueprint parser; contains markdown-parser and snowcrash sources; also contains new PEGTL grammars
• ./packages/apib/ - API Blueprint definition; only contains media type definition now
• ./packages/drafter/ - Drafter C library libdrafter, Drafter CLI drafter-cli
  • PEGTL grammars moved from ./src/parser/* to ./packages/apib-parser/src/grammar/
• ./packages/boost/ - external production dependency
• ./packages/variant/ - external production dependency
• ./packages/cmdline/ - external production dependency of drafter-cli
• ./packages/PEGTL/ - external production dependency of apib-parser
• ./packages/sundown/ - external production dependency of apib-parser
• ./packages/Catch/ - external test dependency
• ./packages/dtl/ - external test dependency

Intent on making the memory representation of our syntax tree available without dependence on parsing logic, I have introduced ./packages/apib/ to contain API Blueprint specific declarations and semantics. Currently it only contains media type definitions moved from ./src/parser, but the intent is to declare new syntax definitions here instead of ./packages/apib-parser/grammar/.

[klokane]

I'm not sure if it is good idea to introduce apib-parser instead of snowcrash. It can be also little bit confusing hold sundown separately from combo snowcrash/markdown-parser

[tjanc]

@klokane

All standalone projects, whether external dependencies or projects developed in this repository, should now be layed out flat in ./packages. The build system should handle the structure of dependencies.

The API Blueprint parser apib-parser is a standalone project. Currently (before this PR) it is composed of:

• sundown, an external dependency
• markdown-parser, regular code somewhere in drafter
• snowcrash, regular code somewhere in drafter

We will be throwing away most of snowcrash and markdown-parser code during the PEGTL rewrite, replacing it with grammars. I want to keep a clean set of dependencies for that precious new code :). So it only makes sense to isolate this logic into a seperate library.

To be honest, adding apib and apib-parser I think is very moderate, and I ended there to avoid bloating this PR.

We should continue splitting up the monolith of drafter introducing apie, drafter-cli next. There is even this old commit from Pavan (10d78fe7a) coming with the comment librefract parts - will be separated into other project in ./drafter.gyp showing the intent of isolating API Elements logic early on.