- prepare_build

- due to new instrument support
- but compression gives almost 20 times file reduction

- when this version become old one

- so do not validate built-in levels

- ask only when user will really need access to any file

- also instrument specific levels from appropriate subdir
- install rules for cmake, NSIS & Android

- get rid of heavy HTML table and text
- use separated QML controls for each level parameter
- added buttons for scaling the preview

when dropped bass clef was detected.

Fixed starting exams/exercises under Win - properly forwarding Tlevel pointer trough QML. Our debug check saved a day by clean it now.

Use Nootka 'one' settings. Fix 'General' group occurrence in settings (it is default name, no need to set group for it in QSettings). Show 'about' window when version changes.

Fixed translation context to reuse as many "older" texts as possible without disturbing the translator.
Some other minor fixes.

- QString always as references
- double QString().arg(,)
- third argument 'this' in connect statement when lambda is used
- full enum names: TclassName::EnumName

Store system font before Nootka set it and use this font for file dialogues to keep their look according to system preferences

Renamed methods and enumerator related to fret to name related to instrument. Also changed asNote to onScore

Increased exam and level version number - it will be not compatible with older Nootka versions any more. Fix executor to correctly close itself when exam file was wrong.

Adjusting fret range to used note range and opposite, allow selecting not suitable levels, to remove them from the list but keep exam/exercise buttons disabled then

Marking levels descriptions of not suitable ones for instrument on red color, selecting last added level, warning about unsaved changes

TlevelCreatorItem exposes level props to creator pages, setting AccidsPage props accordind to loaded level, reactions for user changes