Gui improvements

Starting from Issue335 I went out and tried to make the whole GUI more robust. By now I don't see this crash happen anymore.

By doing this I also almost made the NSXTool to almost support multiple Experiments (as a side effect). As long as files are not saved or loaded this seems to work rather well. I also adapted by previous tables on SubframeHome to support this.

Additionally I implemented a Menu toggling system - similar for some of PushButtons. Now Certain Menu items are only enabled if it makes sense like you need to create an experiment first before adding data files etc.

The menu entry for "Save All" remains disabled since the method behind it is not implemented yet

I also took the liberty to add some Shortcuts for the File-Menu (only default short cuts).

Fixed a bug with the enabling of the "Assign selected unit cell" - Button in Subframe::Indexer. Now one entry from Solutions table need to be selected first.

Fixed a bug SubframePredict regarding auto generated names for PeakCollections now using the foreseen naming scheme.

When creating an Experiment a auto generated name is now suggested in the dialog like in the previous update.

Additionally I really grown tired of always entering the values for Omega and Wavelength when adding raw data. Now the system is looking for a readme file in the directory and tries to read the data for these two parameters from it and then (again) suggests it to he user. I do realize this is completely unasked feature, but this automation takes away some tedious work when looking for crashes and better results. This feature can be removed very easily. Please tell me if I should do so.

and I haven't rebased this yet .. there is some more work todo here