Collator Cleanup

Cleaned up a style issue with some code in collator.cpp.  A variable was initialized, used once on the following line, and then never used again, making the line initializing it and giving it a name completely pointless.
Remove Unneeded Header

Removed the include directive for unicode/normalizer.hpp from unicode/string.hpp.

Historically unicode/string.hpp used an enumeration defined in unicode/normalizer.hpp, but this is no longer the case.
Documentation

Added documentation to the half-documented collation-related types in unicode/codepoint.hpp.
Add UCD Fields

The CodePointInfo structure now contains the Ideographic, Unified_Ideograph, and Radical properties from the UCD.

The UCD parser now parses these properties from PropList.txt.
Collator Weight Derivation

Finished implementing weight derivation for unknown code points.