add /loadalign load with player orientation; add reporting of missing mods to /load and /allocate

1. add /loadalign load with player orientation.

One potential problem is the new /loadalign code hasn't been tested with old-format schem files (ie prior to version 4), but should work. If it doesn't, an option for slightly more robust (but slower) code for rotating individual nodes is included. Worst case if /loadalign fails totally with these versions the original /load can be used, as this function has not been changed.

After doing this I realised it would probably have been easier to use existing code and set it up as sequential save1(temp space for load2/flip2/transpose2), set1=air, load2(into 1), flip2, transpose2, load1(back in) operations, but I didn't think of it earlier, it would have been slower, and it would have been a bit of a hastle saving and restoring the regions the loaded region damaged as it moved through.

2. add reporting of missing mods to /allocate (to version 4 files only). It's also added for /load and /loadalign, but is hidden by errors caused by attempting to add nodes from missing mods (:-(

The worldedit notification message displaying the missing mods is displayed correctly when /allocate is used. However if /load or /loadalign is used, display of the warning is followed by an ERROR[main], which warns a 2nd time about the problems with the nodes. This means that the user probably won't see the message displaying missing mods as unless there are only a few incorrect nodes, the chat message will already have moved off the screen :-( 
The easiest way to sort this will be to block attempted placement of unknown nodes (which I will add to the commit in the next few days). Other possible options would be to trap the [main] error so it wasn't displayed (if it's even possible from lua). Another could be to spawn a process which could display the message until after the [main] errors had been displayed, then show it...