Revamp READMEs

Revamp the version number

Revamp version number (0.1.9)

Add enslave Camera mode

Fix release procedure document

Fix keyboard shortcut issue

Add FoV button to the toolbar of Scene View

Create dedicated script file for EditorWindow

to avoid the following problem
https://forum.unity3d.com/threads/error-loading-window-layout.430751/

Unity 5.5 (?) needs that both of class name and script filename are matched.
Therefore, nested class for EditorWindow should be avoided :(

Update README

Add GUI setting window's description