Initial commit.
Project structure after yandex-contest-invoker split.
unistd::Fstab: begin()/end() implementation.
lxc::LXC::prepare() integration with unistd::Fstab begin()/end().
unistd: kill() and kill0() implementation.
unistd::info boost::error_info typedefs.

unistd operations provide their arguments as additional error data.
Control Group draft partial implementation.
cgroup partial implementation.

Virtual inheritance was introduced for subsystems
instead of CRTP for controlGroup() member function.

ControlGroup (partially implemented):
    *) readFieldByReader()/writeFieldByWriter() implementation.
    *) remove()/terminate() became noexcept(false) (may throw).
    *) Constructor refactoring.
    *) terminate() implementation.

getMountEntry() implementation.

Various subsystems improvements.
unistd::rmdir() implementation.
cgroup::ControlGroup implementation.

*) ControlGroup()/remove() implementation.
*) readStringField()/writeStringField() were replaced
   by readField()/writeField() explicit std::string specializations.
*) readField<std::string>() will call trim_right() on read data.
*) readFieldByReader error handling bug fix.
*) tasks() implementation improvement.
execution::AsyncProcess::pid() implementation.
cgroup::ControlGroup::{create,terminate} tests implementation.
cgroup::ControlGroup improvements.

Not-owning constructor implementation.
attach()/detach()/close() implementation.
Logging improvement.
cgroup::ControlGroup::parent() implementation.
unistd::{getpid,gettid}() implementation.
cgroup::ControlGroup::fork_bomb test implementation.
cgroup::ControlGroup::remove() bug fix.
cgroup::ControlGroup refactoring.

attach(pid_t) -> attachTask(pid_t).
cgroup::ControlGroup: getControlGroup()/getControlGroups() implementation.
cgroup::ControlGroup move-semantics implementation bug fix.