8.26 BRANCH ONLY - REVERT THIS ONCE MERGED TO TRUNK

XAS-63 - show the X and Y position of the mouse when over the LivePlot

This will only work in 8.26 as it has a hard coded cast which bypasses
the SciSoft API so will probably break in the future.
Simple Scan: Stop now calls scannable stop as well as motor stop. Num
pad enter works as well as ordinary enter.
DAServer: Added check to make sure buffer size returned from daserver is
the correct size
Removed unnecessary read of frames twice
Merge branch '8.26' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-core.git into 8.26