Mostly fixes

Release Notes 1.15.3

New

• Added new --import command-line option for importing directly from command-line.
• Added support for importing Markdown.

Changes

• Removed --format command-line option in favor of new --import and --export options.
• Improved export of Markdown output.
• Improved loading of Minder Markdown syntax highlighting to make this an application-only syntax (not user-wide).

Bug Fixes

• Fixed Markdown export issue with root nodes.
• Fixed issue with inserting non-printable characters.
• Fixed issues with cursor movement for RTL languages.
• Fixed issue with using Control-W shortcut when only a single tab is shown.
• Fixed potential issue with adding a new tab.
• Fixed issues with tab naming of new, unchanged documents.
• Fixed cursor/selection issue when the Delete key is used (includes application crash issue).
• Fixed issue with Control-Up cursor selection shortcut.
• Fixed issue with centering a node with Shift-C.
• Fixed several issues related to zoom/scaling.