Log Message:
texstudio: update to 2.12.6

- use Breeze window theme on KDE Plasma 5
- support single-finger panning gesture on most config dialog components
- support single-finger panning touch gesture on log viewer
- pdf viewer scroll tool: support single-finger panning gesture
- center width-constrained documents in the editor (optional)
- add document tab context menu entries "Close" and "Close All \ 
Other Documents"
- improved layout of config build page
- add system check for language tool
- change search defaults to case-insensitive (feature-requests#1254)
- tags for beamer
- change preview default to embedded pdf
- handle preview failures more gracefully, i.e. no warning pop-ups
- repect preview settings (panel,etc) also for hover preview
- show hover preview as tooltip in case of inline-mode
- warn if compiler commands are actually a command list
- several improvements to the latex parser
- notify that a restart is required when switching between modern and
  classic style
- improved LanguageTool communication: better error handling
- add reset to default button for some LT settings
- add 200ms delay before showing auto-hidden viewer toolbar to prevent
  flicker
- eye candy for pdf circular magnifier (adapted code from texworks)
- show pdf highlight in magnifier
- capslock does not close completer any more
- alternative approach for determine directories from complete texts
- use cache for previews
- auto open completer when starting to type in references, packages etc.
- scripting: editor.cutBuffer
- subframetitle in structure view
- enable inputMethod (e.g. ^) in completer
- change default for complete non-text chacters to off, as it tends to
  cause unexpected behaviour
- bug fixes