Rewrite HttpObjectDecoder to make use of proper state machine

Motivation:

HttpObjectDecoder extended ReplayDecoder which is slightly slower then ByteToMessageDecoder.

Modifications:

- Changed super class of HttpObjectDecoder from ReplayDecoder to ByteToMessageDecoder.
- Rewrote decode() method of HttpObjectDecoder to use proper state machine.
- Changed private methods HeaderParser.parse(ByteBuf), readHeaders(ByteBuf) and readTrailingHeaders(ByteBuf), skipControlCharacters(ByteBuf) to consider available bytes.
- Set HeaderParser and LineParser as static inner classes.
- Replaced not safe actualReadableBytes() with buffer.readableBytes().

Result:

Improved performance of HttpObjectDecoder by approximately 177%.
Benchmark for HttpRequestDecoder