implement "-c" option to allocate a number of CPU shares to a container

Upstream-commit: efd9becb78c82ddef07efb7e76e0100d7a712281
Component: engine

components/engine/docs/sources/commandline/command/commit.rst

@@ -16,6 +16,7 @@ Full -run example::
 
     {"Hostname": "",
      "User": "",
+     "CpuShares": 0,
      "Memory": 0,
      "MemorySwap": 0,
      "PortSpecs": ["22", "80", "443"],

components/engine/docs/sources/commandline/command/run.rst

@@ -9,6 +9,7 @@
     Run a command in a new container
 
       -a=map[]: Attach to stdin, stdout or stderr.
+      -c=1024: CPU shares (relative weight)
       -d=false: Detached mode: leave the container running in the background
       -e=[]: Set environment variables
       -h="": Container host name