Fixes #19: 'Save Structure' and 'Copy As' items are now functional in the Windows Explorer context-menu. This fix also includes some code cleanup and refactoring because the same commands are also available in preview context-menu.
Fixes #47: SSSR property is now available for MOL, SMI, SMILES and SMARTS files.
Fixes #48: A warning icon is now shown on the preview window when there are chemical warning for the current molecule or reaction. Two warnings can be shown - Valence and AmbiguousH. Moving the mouse pointer over warning icon displays a balloon tooltip with warning text.