SERVER-6399 Added support for parsing dotted fields.
SERVER-6399 Fixed memory allocation in Field Ref.
SERVER-6399 Simplified FieldPart class.

Conflicts:
	src/mongo/db/ops/field_ref.cpp
SERVER-5710 Changed KeyPattern.hasField() sematics to consider dotted field prefixes.

Conflicts:
	src/mongo/SConscript
	src/mongo/db/ops/update_internal.cpp