Generic linear solver for upper triangular matrices
Redefine generic solver to avoid ambiguity
Add zeros, ones, infs and nans methods taking an AbstractMatrix argument
Add generic solver for Triangular{T} matrices

- Generic inverse replaced with generic solve on identity matrix
Provides cond(A::Triangular)

- wraps LAPACK wrapper trcon!, reciprocal of condition number estimate for triangular matrices
- type stability bugfixes to generic cond()
- Triangular-specific tests for linear solver and cond()