Compiler Refactor

We have compiler constants defined in, but not related to DSASM namespace.  They are moved to the appropriate compiler namespace

1. Move compile pass constants from DSASM to
ProtoCore.Compiler.Associative and ProtoCore.Compiler.Imperative
namespaces
2.  Move accessspecifier constants from DSASM to
ProtoCore.Compiler.AccessSpecifier namespace

Requires no tests as there are no semantic changes

@ke-yu @lukechurch 
I'd suggest not using bitwise operation, see [FlagsAttribute] (http://msdn.microsoft.com/en-us/library/system.flagsattribute(v=vs.110).aspx). So for this case:
```
[FlagsAttribute]
public enum OptImperative
{
    kAutoAllocate = 1
    kInferTypes = 2
}
...
var options = OptImperative.kAutoAllocate + OpImperative.kInferTypes;
```
BTW, 
  1) name ``OptImperative`` suggests it is imperative, so should it be in imperative namespace?
  2) I don't see where this one is used?