Properly handle statfs on FreeBSD

* FreeBSD doesn't need statfs64 as regular statfs uses 64 bit types
* FreeBSD uses different headers for statfs
Add desktop file
Add installation support to cmake
Fix variable name
Followup on invalid panel path err. All test cases work now.

This is followup on my commit of 2014-08-27.
- c3 test case is passing. The case is app startup with panel saved path on removed USB drive. Funny dialog seqience shows up when both saved panels use the removed USB, though everything works.

- Fixed regression bug from the last change: not showing any message when attempting to enter inaccessible folder.
Merge pull request #62 from AMDmi3/statfs

Properly handle statfs on FreeBSD
Merge pull request #63 from AMDmi3/install

Add installation support to cmake
Merge pull request #64 from helgp/master

Followup on invalid panel path err. All test cases work now.
Merge branch 'master' into stl

Conflicts:
	wcm/fileopers.h
	wcm/panel.cpp