Refs #11035 use Path:: for paths that are defined in config. Except for Log & absolute paths... they need more work.

Fixes #10705. New function 'HelperFile::joinPathFilename($pre, $post)'. Joins only if $post is without leading slash.

Fixes #10177: Fill STORE_RECORD directly after form INSERT/UPDATE - '{{id:R}}' is now usable in processing Glue inserts.

Implements #9679: formModeGlobal is now also used via STORE_USER - set formModeGlobal systemwide for a specific user (session).

Implements #9617. a) formModeGlobal=requiredShowOnly set's the form attribute. The new STORE_VAR 'allRequiredGiven' is set

PDF/fileSplit: uploaded PDF file with missing extension '.pdf' have not been recognized as PDF files - fixed.

splitPdf: using 'fileSplit=jpeg' and uploading a PDF with only one page, results in split.jpg. Now, split.jpg is renamed internally to split-0.jpg to provide a repair shell script a unified naming scheme.

Fixes #7925. a) change CWD during split reduced to splitting only. b) fixed problem in mkDirParent() with absolute paths, c) make logger independent of CWD, d) fixed problem with `mktemp --tmpdir`(difference Ubuntu 16 / 18) by using PHP function, e) fixed some 'undefined index' problems