Define .barracuda.cnf variable for "reserved" memory

Given that BOA is mostly used for the services Omega8 offers, I'm throwing this one up here to see if there are others who might find value in it.

Since I'm using my box for a few other services, one of which is a Java based confluence install, BOA's assumption about max memory and setting these requires a post update script or manual process on updates.

Because my Confluence/Java uses a percentage of memory on the box, the apc.shm value is automatically set too high and has to be reduced - otherwise I get segfaults from php.

With something like _SERVER_RESERVE_MEMORY you could specify an amount that BOA would account for and reduce it's auto calculations for memory settings.

This would allow BOA to comfortably live on the box for those of us foolish enough to run other processes. ;)