Add specialisations that return scalars

[Ericgig]

Add functions that return properties or measurement of the data layer:

properties: isherm, isdiag, iszero. measurements: expect, expect_super, inner, inner_op. norm: one, trace, max, l2, frobenius.

jitting expect give a nice 100x speedup for small (100x100) matrices.

[coveralls]

Pull Request Test Coverage Report for Build 3251506886

• 106 of 106 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 95.925%

---

Totals
Change from base Build 3204692475:	0.2%
Covered Lines:	306
Relevant Lines:	319

---

💛 - Coveralls