Make it complie with 26 without logger
session: added parallel lookup method
elliptics: initial v2.26 implementation
log: elliptics node writes its log intormation into standard Go log.Logger now
session: implemented prepare/write/commit methods, use io.Reader in upload

These methods are used for large file upload - we prepare enough
space on disk, put multiple chunks into the file and then
commit desired size. Default chunk size is 10m, files less than that
are read into memory and uploaded via common write_data() method.
Reading from io.Reader can return less than maximum chunk size,
we start writing data into elliptics as soon as there is something.

Since upload methods are now using io.Reader they do not buffer
too many data, at most chunk side per goroutine.

Returned channel yet contains a mess of combined json objects each
per written chunk, this will be cleaned next.
chunk-write: only put the last write result, i.e. the one after commit message, it contains correct information
Merge branch 'v2.26' of github.com:bioothod/elliptics-go into bioothod-v2.26

Conflicts:
	elliptics/gologger.cpp
	elliptics/logger.cpp
	elliptics/node.cpp
Merge branch 'bioothod-v2.26' into 2.26
session: switched to uint64_t instead of size_t. Added offset/size read/write parameters.
session: added GetGroup(), store groups in local session. Added chunked read and streaming read interface, which streams data into http pipe
node: extended default logger format
node: increase default number of io/net node's threads. Fixed blackhole log formatter.
node: fixed node creation check, return error if not could not be created
Merge pull request #11 from bioothod/v2.26

2.26: new API and bugfixes
Bugfixes and tests.

Bugfixes:
 - Node.AddRemotes: returns error in case of an empty array of remotes

Test coverage: 14%
Enhancement of API. Export DNET_IO_FLAGS and DNET_FLAGS

Enhancement:
 + Added getters for Cflags, IOflags, Timeout, TraceID
 + Set/GetTraceID, Set/GetIOflags, Set/GetCflags accept a custom type
 instead of uint32_t/uint64_t
 + cflags, ioflags are hidden under typedefs

Testcoverage:
 + 15%
Fix travis.yml: install go cover tool
Hey! Travis, build with go1.3
TestCoverage: 76%
stream: only set size to total_size if client set it to 0