CasualConc update

I got a couple of bug reports and a feature request, so I fixed them and add the feature. I also found some other bugs related the reported one and fixed them too. In addition to them, I made one minor change.

Bug fixes
- crash in Concord with Scope of Context set as Sentence in the Database mode.
- corrupted export CSV files from Collocation
- crash in saving Collocation table

Addition
- Reverse Alphabetical sorting in Word Count

What this does (if it works) is to sort words in alphabetical order, but from the last letter to the first letter. So in the normal alphabetical order, a, an, that, the, this are ordered in this order, but in Reverse Alphabetical order, the order will be a, the, an, this, that.

Change
- settings of minimum frequency in Cluster, Collocation/Coocurrence, and Word Count are moved to Preferences

Now you can't set Min Freq. for each table in Cluster and Word Count, but CasualConc remembers the Min Freq. for each tool.


I also got a request to support exporting results in Excel format. I've been experimenting this and this is on the to-do list (I can't tell you when I will add this because I need to figure out how to implement this first). This would probably require you to install a Ruby Module in Terminal (a single line of command). Is there any other people who are interested?