TAIDL v2.15

Changes since v2.14, the documented semantics and the literal checks:

• Documented a spec's integers, attributes, element types and kept names (#144)
• Reworded the documented semantics in plainer sentences (#145)
• Refused an integer literal outside the 64-bit range and a division by a literal zero (#147)
• Added NOTICE (#148)

What changes for specs and generators:

• A spec with an integer literal outside the signed 64-bit range no longer loads. Nor does one with a / or % by the literal 0.
• The call that reads the faulty text raises SyntaxError, naming the place, line and column:
  • add_instruction and add_constraints, for a constraint or an update
  • set_inputs and set_outputs, for a start or a size
  • add_semantics, for a semantics
• docs/expressions.md now states that every integer a spec reads or computes is a signed 64-bit integer.
• It also states that an addressing attribute appears only in a region's start and in a constraint.
• docs/semantics.md now names the presumed reshape: a region's value of another shape but the same element count is held in the region's shape.
• The grammar and the generated parser are unchanged. So is every name the package exports.

This release:

• The version is 2.15 in pyproject.toml and taidl/__init__.py. The README's install line names v2.15.
• NOTICE names the copyright of the ACT contributors and the software developed at the University of Illinois Urbana-Champaign.