Further memory management improvements

[Russell Taylor]

If we run into issues down the line with memory fragmentation, there are a number of strategies we can employ to try and improve this.

• We can use a Low Fragmentation Heap in Windows.
• In Linux, we can change the M_MMAP_THRESHOLD parameter of malloc using mallopt to obtain large chunks of memory (i.e. MantidVecs) using mmap, so that they'll be located separately in memory and released to the kernel when a workspace is deleted.
• We can write a custom Allocator to use with the workspace data storage that uses mmap/munmap on Linux and VirtualAlloc/VirtualFree on Windows to keep the workspace data in a separate area of memory that shouldn't get polluted by other 'little' objects.

[Nick Draper]

Moved as part of iteration 18 end

[Nick Draper]

Moved as part of the end of Iteration 19

[Nick Draper]

This work has already been done on another ticket

[Stuart Campbell]

This ticket has been transferred to github issue ​1566