Pull ANN Library into Kernel

[Michael Whitty]

The ​Approximate Nearest Neighbour Library is required for use in determining the nearest neighbours of a detector in instrument geometry.

Rather than building this and including it as a separate dependency, we will add it into the Kernel.

ANN is licensed under the ​LGPL, so we should not have any copyright issues. However, must remember to credit it in the documentation.

[Michael Whitty]

(In [7742]) refs #1998 - placing ANN library into Kernel

[Michael Whitty]

(In [7743]) refs #1998 - adding ANN directories to Doxygen ignore list.

[Michael Whitty]

(In [7744]) refs #1998 - adding *correct* ANN directories to Doxygen ignore list.

[Anders Markvardsen]

Done and ANN credited where used in code

[Stuart Campbell]

This ticket has been transferred to github issue ​2845