Expand GroupWorkspaces to allow grouping of table workspaces

[Anders-Markvardsen]

1. Modify the algorithm GroupWorkspaces to allow this
2. Do a test. Group say a TableWorkspace and a standard MatrixWorkspace.
   Try to run this grouped workspace through a number of Mantid algorithms such as Minus and CropWorkspace. Likely outcome is that error messages will be displayed which needs to be dealt with. Initially the way do deal with these will be to modify how algorithms handle groups. E.g. Algorithm.cpp has a method: bool Algorithm::processGroups(). Modify this method to ignore TableWorkspaces and log this.

[Anders-Markvardsen]

This issue was originally trac ticket 4055