Jam: various improvements and fixes

Summary:

• fix x=: is a rule named x=, not a variable
• fix exe onxxxxx: is a rule call, not a variable
• fix ifxxx, rulexxx, etc: not keywords
• fix variable default = xxx ;
• fix keywords and operators in a condition: they must be separated by spaces
• fix on target
• fix switch
• fix class and module
• fix for local x
• new styles: Feature and FeatureOperator for <xxx>, -<xxx>, <xxx>abc:<yyy>abc, <xxx>abc/<yyy>abc, <xxx>abc&&def
• don't use black color in Rule

Reviewers: Framework: Syntax Highlighting, dhaumann, cullmann

Reviewed By: Framework: Syntax Highlighting, dhaumann, cullmann

Subscribers: kde-frameworks-devel, kwrite-devel

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D21508