add window min/max/resize

[akvadrako]

This does a couple things:

• allows one to specify an optional min/max window size like this:

  export COG_PLATFORM_FDO_VIEW_HEIGHT=100:300:500
  export COG_PLATFORM_FDO_VIEW_WIDTH=100:300:500
  

• allows one to resize a window with cogctl:

  ./cogctl resize 0:500:0x0:500:0
  ./cogctl resize 100x200
  

In the end I want to do this from the client side, but I thought for a now a clean way is to add it do cogctl. Probably I'll use a local HTTP server than can call cogctl for privileged operations.

It could use a bit of docs and maybe some refactoring. I'm also not sure if this is something you want to have in cog, so I could fork it if that's preferable.