Changing keywords in CLS

Featuring:
+ delta
+ digits
+ refinement (in addition to refine, but replacing refine in many places)
- template (useless now)
- test (will reconsider as a different approach is available, but not needed now)
Adding a label to pattern matching chapter of CLS
Updating chapter about classes and objects in CLS

Featuring:
- refinements syntax
- added missing indexing parameters and units of measure parameters to class definitions (previously were in separate sections)
- updating section about case classes
- adding missing units of measure parameters to trait definitions
- updating syntax of protocols and interfaces
- updating section about object definitions (incomplete)
- fixing constrained types section
Fixing function types in types chapter in CLS
Updating chapter about types in CLS

Featuring:
- syntax of types overview at the beginning of the chapter
- fixing parameterized types definition (was missing units of measure)
- updating section about compound types (with refinements)
- fixing function types
- updating existential types to allow `val` and `var` declarations as well
- fixing syntax of dependent types (Dep_Type was never used, Simple_Type is the thing)
Updating section about boolean literals in CLS

Featuring:
- explicitly specifying that boolean `no` and value `nil` are not interchangeable in pattern matching
Changing link style in preface of CLS