- piqi_tools.erl -- initial implementation of Erlang bindings for Piqi tools
  using Erlang port interface and "piqi server"
- New top-level directory for Piqi-RPC -- an RPC-over-HTTP system for Erlang.
Working on piqi-rpc...
- Made several Piqi-RPC errors for different error types instead of having one
  string for all.
- Finished initial versions of Piqi-RPC skeleton generator and runtime support
  library.
- Started working on HTTP part of the server.
- added another "invalid_output" RPC error which corresponds to "502 Bad
  Gateway" in HTTP.
- encoding Piqi-RPC errors to HTTP response (basically, a combination of HTTP
  status code, body, and Content-Type header for each type of Piqi-RPC error).
Integrating various Piqi-RPC components (work in progress).
More work on Piqi-RPC:
- Determine output "Content-Type" based on "Accept" header.
- Special handling of non-exported Erlang impelmenentation functions instead of
  crashing.
- Fixes in generating implementation specs and default implementation functions.
Working on Piqi-RPC service initialization, management and availability:
- Monitor, automatically restart and re-initialize Piqi tools.
- Central RPC service registration and status tracking.
- Report HTTP status 503 "service unavailable" when appropriate.
Working on Piqi-RPC: improving service availability and avoiding races.
- Integrating Piqi-RPC: more improvements and fixes.
- Added a new Piqi-RPC "service-unavailable" error (aka HTTP 503).
- Added proper Erlang OTP packaging and high-level interfaces for Piqi-RPC
  application.
- Moved Piqi-RPC interface compiler plugin (piqic-erlang-rpc) and examples to
  separate directories.
(piqic erlang) Add "_piqi" suffix to generated ".erl" and ".hrl" files.
- Wrapped "piqic erlang" call into "piqic-erlang-rpc" to simplify things and
  prevent generated modules from going out of sync.
- Reverted back to using 1-arity Erlang functions for Piqi-RPC service
  implementation in case of no input (was 0-arity).
(Piqi-RPC) Use "application/x-protobuf" instead of "application/protobuf" as a
Content-Type.
Added the ability to initialize Piqi types without calling
"piqi_tools:add_piqi()" explicilty. This allows to run "piqi_tools"
gen_server independently from a specialized "piqi_rpc_monitor" supervisor.
- Renamed "piqirun-erlang" top-level directory to "piqi-erlang".
- Renamed "piqirun" Erlang library application to "piqi".
- Moved "piqi_tools.erl" module to "piqi" application.
- Updated all the dependent code to use the new names and paths.
Simplified Piqi-Erlang codecs interface:
- Now it is possible to use parse_<type>/1 directly on binaries without callinng
  "piqirun:init_from_binary/1" first.
- Now it is possible to use gen_<type>(X) instead of gen_<type>('undefined', X).

NOTE: this change is backward-compatible with the code using the old interface.
Fixed a minor build problem.
Compatibility with Erlang/OTP R13.
- Removed all non- OTP-compliant supervision and trickery.
- Added OTP-compliant supervisor and application behaviors to "piqi"
  application.
- Moved some files around for better directory and component layout.
- Now piqic-erlang-rpc compiler reuses code from piqic-erlang-ext which now
  comes as a part of the "piqi" Erlang application.