Support intelligent re-quoting / entangled quoting.

While it was never an issue in C/C++ because quotes are tied to char and string datatypes, other languages like JS and Python do not make a distinction between quotes. However occasionally the need arises to re-quote a string, anecdotally when working with SQL. and a value needs to be included where it hasn't been previously. 

'SELECT X FROM T' + where clause = 'SELECT X FROM T WHERE Y='VALUE' '

At this point the statement cannot be properly parsed. The outer quotes need to be changed to " 

It is not expected that QtCreator detect this conflict, but having the user select text, or even just the starting or trailing quote, and changing the quote character should produce a change at the other quote:

Cases: [ ] indicate selected characters:

'[this is some text]' + " = "[this is some text]" (as opposed to "'[this is some text']'"

[']this is some text' + " = "this is some text" ("entangled quotes")

']this is some text['] + " = "this is some text" ("entangled quotes")

[this is some text] + ' = '[this is some text]' (goto first example)

There is some ambiguity where behavior is not well-defined, but I think we can find a sensible behavior:

'SELECT X FROM T WHERE Y='VALUE''

The challenge is do we pair the first and second or first and last quotes? I think if we define start and inner quotes, we'll get an intelligent answer.

'C  - start  quote

C'C - inner quote

C' end quote

So the text within the span of change is the mating quote as defined by a stack of start and end quotes, with inner quotes ignored unless it's he last quote.  So the following examples will work:

'SELECT X FROM T WHERE Y='VALUE'' - start inner inner end

'SELECT X FROM T WHERE Y = 'VALUE' ' - start start end end

'SELECT X FROM T WHERE Y = 'VALUE'' - start start inner end

We do have do define C a little bit because a commas should not change the quote:

'string 1','string 2' != "string 1','string1",  instead == "string 1",'string 2'

Of course, these are not hard rules, they are just to describe the desired outcome.