Dependency Version Ranges

Need to be able to declare minimum, maximum allowed versions of a dependency (both min and max may be optional), and allow "holes" for known incompatible versions.

Proposed syntax:

Range	Meaning
(,1.0]	x <= 1.0
1.0	"Soft" requirement on 1.0 (just a recommendation - helps select the correct version if it matches all ranges)
[1.0]	Hard requirement on 1.0
[1.2,1.3]	1.2 <= x <= 1.3
[1.0,2.0)	1.0 <= x < 2.0
[1.5,)	x >= 1.5
(,1.0],[1.2,)	x <= 1.0 or x >= 1.2. Multiple sets are comma-separated
(,1.1),(1.1,)	This excludes 1.1 if it is known not to work in combination with this library