SERVER-15089 cleanup oplogreader

1. Move some master/slave oplogreader code into master_slave.cpp
2. fix up includes for some files; remove pch.h from a header (!)
3. remove awaitCapable check
4. add new "_host" field to oplogreader to store the HostAndPort we're connected
to; will be used by new Applier
SERVER-15062 test ElectCmd in the ReplicationCoordinator
SERVER-15062 test FreshCmd in the ReplicationCoordinator
SERVER-15147 move Date_t and OpTime ostreaming to unittest
SERVER-14931 fixed current command shell command length to take into account multi-byte characters

Closes #765

Signed-off-by: Benety Goh <benety@mongodb.com>
Merge remote-tracking branch 'upstream/master'