Bash: fix parameter & brace expansion

Summary:
BUG: 387915

Sometimes, the content in braces { ... } is not correctly highlighted, since the RegExpr rule that detects it is very general.

Also, some parameter expressions are added, such as ${parameter^^pattern}, ${parameter,,pattern} & ${parameter@operator} (before, that was highlighted as "Error"). In the expressions ${parameter:offset:length}, spaces are allowed after ":" and +/- signs in numbers.

Source:

• Bash Reference Manual: https://www.gnu.org/software/bash/manual/bashref.html#Brace-Expansion

Reviewers: cullmann, dhaumann, Framework: Syntax Highlighting

Reviewed By: cullmann, dhaumann, Framework: Syntax Highlighting

Subscribers: kwrite-devel, kde-frameworks-devel

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D15390