Release v0.15.0

This release is a major roll-up of many incremental enhancements.
Note that the Builder is separately downloaded from the GUIslice-Builder repo

Changes since 0.14.0:

• Enhance: major updates & improvements to the Builder (download separately from the GUIslice-Builder repo)
• Add: widget: XTogglebtn
• Add: widget: XSeekbar
• Add: Touch driver for RA8875_SUMO
• Add: Display driver support for Wavershare_ILI9486 v2
• Add: dynamic element moves #246
• Add: background redraw for modeless dialogs #227
• Add: dynamic updates for XListbox
• Add: API for XKeyPadInputGet() to return string
• Fix: color conversion #219
• Fix: XSlider range #238
• Fix: pin-sharing with 4-wire touch (Due, Nano 33 IOT)
• Fix: compilation warnings
• Enhance: optimize redraw for ElemSetCol, ElemSetGlowCol
• Change: API for XCheckbox to always return its ID #244 (see migration notes)
• Enhance: debug messaging for element creation

Migration notes

• A minor breaking change was added to XCheckbox (for #244). This only impacts a minor subset of users that are detecting a checkbox disable event action. If the user code has a checkbox callback function that tests for nSelId == GSLC_ID_NONE and then determines which checkbox was responsible for this event (via pvElemRef), a simpler method is now available: determine the checkbox that triggered an event (via nSelId) and then test the bChecked state.