Added mouse drag detection threshold.

This considerably reduces CPU load while dragging container view.

Note that the threshold is only used when drag occurs on title container view, but even restructured code as it is, results in much smoother operation for most frequent cases where underlying window intercepts the drag.
Disabled window buttons now respect their style when window is not focused
Adjusted corner raidus and document/version/dash alignment
Merge branch 'master' of github.com:tomaz/INAppStoreWindow
Merge branch 'master' of github.com:pfandrade/INAppStoreWindow