v0.2.0 release

• added possibility of selecting multiple notes in the tree (shift+up/down or ctrl+click) and things like copy&paste or drag and drop now work with selected items (behavior should be the same as before when working with single item).
• changed keyboard shortcut because of multi-select - shift+arrows formerly moved notes around. This is now done with ctrl+arrows. shift+up/down is now used to select multiple notes.
• better detection of tree cycles when cloning/moving notes around. Also added consistency check.
• context menu has now option to force sync for one note
• various small bugfixes