Allow specialised User interfaces for specific Algorithms

[NickDraper]

This should allow specialised user interfaces to be created for a limited number of algorithms.

This will have to include:
- A suitable interface or base class that all specialized user interfaces inherit from.
- A dynamic factory class (see kernel) that allows the user interface for a algorithm to be created.
- Final cleanup is to replace the hard coded LoadRaw dialog that the Load button uses.

Again this should remain independent from qtiplot, although it can of course use QT and mantid

[NickDraper]

This issue was originally trac ticket 444