Add shortcuts for raise/lower/bring to front/back for composer, fix some other composer shortcuts
optionally use base url for WMTS GetTile requests (implements #8595)
Switch composer select/move icon to more appropriate icon
Remove redundant composer selection tolerance setting
Increase number of allowed open files on Mac

- Increase from default 256 to 4096-to-8192 range, or OPEN_MAX for process
- From code provided by Larry Biehl, Purdue University, USA, from 'MultiSpec' project