master: Add IoLimitsDatabase

Add a class which stores information about global I/O limits.

Change-Id: I99563e41ebf6024cad0876703aa628e4283a3a7c
master: Support registration of I/O limited mounts

Detect clients that support I/O limiting and register them in
appropriate data structures.

Change-Id: I15b3d5c7b181f4f22fa848f902d122b725ff6990
master: Support I/O limit negotiations

Allow clients to negotiate changes in their I/O limits.

Change-Id: I0db7b27710ab2d8da5fda3df442c20a0f2125d35
mount: Support LIZ messages in mastercomm and masteproxy

Make it possible to send and receive new messages in mount and tools.

Change-Id: I6b91f5c2bf94c884abc547b442db1e6f6b675d81
mount: Refactor mastercomm

Make mastercomm suck less:
- decopypastify the legacy MooseFS code
- create a typedef for message buffers
- use vectors instead of arrays for outgoing packets
- remove pointless copying of outgoing LIZ packets

Change-Id: I85f78465d4384bd1f00f9f51bb504f9fd71c4bbb
metarestore: Fix applying single line changelogs

Mfsmetarestore couldn't read the number of the last change in
changelogs with only one line and assumed it was empty.
This commit fixes it.

Change-Id: Ibed0ca6064761993bc6e0cd4c073b6d3a55bbf6d