v1.513: better CSV file support, UI changes/fixes

  DX label CSV file import: commas are now an accepted field delimiter character.

    String fields are not required to be quoted (unless they contain the delimiter character).

    Spreadsheet CSV file write compatibility should be increased with this change.

  Mobile devices:

    The double-finger-tap menu (right-click menu on desktop) now highlights entries

    as you swipe over the menu. Just as the desktop menu does when swiping with the mouse.

  Added SAM PLL "Reset" button on audio tab. Use when the SAM PLL has wandered outside of its

    capture range. The previous workaround was to switch to AM then back to SAM to reset the PLL.

  Admin page, config tab: option to set 1Hz frequency display resolution.

    Will eventually be a user control panel option for this, but that will have to wait for

    a general redesign of the control panel.