improve ctor and dispose

[bollhals]

PR 6 extracted out of #40

Focused on the Ctor & Dispose methods

Main change:

• Preallocate some space for the dictionaries so they don't have to do this on the first resolve.
• Avoid closure allocation on dispose

Performance measurements:

For the first point it's hard to show benefits, except that preallocation is faster than grow the internal size of the dictionary multiple times.

For the 2nd bullet I've created a small test that just dispose the container, but I haven't added it, as I do not believe it really adds much value, but for the sake of completness:

Method	Mean	Error	StdDev	Min	Max	Median	Rank	Gen 0	Gen 1	Gen 2	Allocated
Current	155.3 ns	1.91 ns	1.79 ns	152.7 ns	158.4 ns	155.2 ns	1	0.0763	-	-	360 B
Master	226.8 ns	1.24 ns	0.97 ns	224.8 ns	228.1 ns	226.9 ns	1	0.1223	-	-	576 B