Faster JclStringList.Join - via StringBuilder
TJCLStringBuilder.Insert typo - compare with .Add
JclStringBuilder should know about TObject.ToString
only use JclStringBuilder is stock one is missed
Making String Contains/Consists set function more consistent:
* CharIsNumberChar should account for ThousandSeparators too, if accounts for DecimalSeparator
Work on #5898 #5893
* StrIsDigit is awful Engrish
* StrIsSubset is nothing but another name for StrConsistsOfChars
* StrIsDigit is nothing but another name for StrConsistsOfChars with proper filters
* StrConsistsOfNumberChars is nothing but another name for StrConsistsOfChars with proper filters
* there are three kinds of checks:
**  target only contains given chars
**  target contains some of given chars
**  target contains (among other) all the given chars
One boolean value was ambiguous to separate those tasks. Now there are three distinct name schemes.
* ToDO : make StrIsDigit and StrConsistsOfNumberChars permit empty strings ???
#0006081 - crash because of dangling pointers and FreeAndNil