Resolves: forge.typo3.org/issues/68523

The problem was when the session is empty, until user makes some selection. In case of empty session (selection not in session), first item of numSiteConstsOptions is selected and saved to session.
Method 'assignViewWidthMenuVariables' does that and sends selection and options to view.

Added a new field below "Select constant type" to make the number of constants to show selectable

Resolves: forge.typo3.org/issues/66188

This is the error message:
"Warning: htmlspecialchars() expects parameter 1 to be string, array given in /var/www/ay.dev/typo3_src-patched/typo3/sysext/fluid/Classes/ViewHelpers/Form/TextareaViewHelper.php on line 65"

I couldnt reproduce bug where label tag in xml file is marked as array, but this would fix that issue.

Resolves: forge.typo3.org/issues/67142

Larger constant name field for:
- add constant
- rename constant and
- search constant

Resolves: forge.typo3.org/issues/65982

Resolves: forge.typo3.org/issues/66183

* When user edits a file, languages from section 'Select up to two languages' are considered as 'edited languages'.
* If some language is not edited, its file will not be rewritten.

* XLF:
- If user edits default language (language from main file), all localisation files will be rewritten, because default language appears in them as source.

* XML:
- If there is one, merged, xml file, this feature is disabled.

Resolves: forge.typo3.org/issues/67499

Bugfixes

See merge request !4

Resolves: #67421

Resolves: #67864

This exception seems to happen if the last constant was removed/changed, because the line in the AdditionalConfiguration still refers to a file, but this file just contains the xml header then.

Using 'xml:space="preserve"' if constant contains LF or multiple space characters in its source or in its target value.

Related: forge.typo3.org/issues/66178

- removing xml:space tag
- not replacing newline with br tag

Updating LFEditor xlf files:
- removing xml:space tag
- replacing br tag with newline

Resolves: forge.typo3.org/issues/66178

Related: forge.typo3.org/issues/66178