[BOOTLIB]: Separate out bcd.c into bcdopt.c, bootreg.c and bcd.c

[BOOTLIB]: Separate out bcd.c into bcdopt.c, bootreg.c and bcd.c
[BOOTLIB]: Implement routines to enumerate subkeys and to read a key value.
[BOOTLIB]: Implement routines to parse, enumerate, and convert registry data into BCD elements, and to convert BCD elements into boot library BCD options.
[BOOTLIB/BOOTMGFW]: Lots of cleanups, mainly around the fact we now use ntintsafe.h instead of the manually self-inlined code from before, and from documenting additional flag values, and from using our newfound BCD powers.
[BOOTMGFW]: Implement BmGetOptionList, BmpUpdateApplicationOptions.
[BOOTMGFW]: Prepare for post-BCD library reinitialization. We correctly read the 3 BCD options so far in the hive.

svn path=/trunk/; revision=70492