ENH: HaloType bitmask to encode different types

HaloType is a singleton class that allows encoding type(s)
corresponding to a halo. For example, a halo could be designated
as a ZOMBIE, a GHOST or both.
ENH: Use HaloType as a bitmask instead of as int
ENH: Prefer namespaces instead of static members
ENH: Integrate SQLite in CosmologyTools
BUGFIX: Fix erroneous GetPackageSources call

Fixed issue wherein the pacakage sources for the common package
were not being properly set. Consequently, the generic-io
code was not correctly being compiled in to the single
monolithic libary, cosmotools.a, when compiled with
BUILD_SINGLE_LIBRARY
ENH: Add GlobalID to Halo data-structure

Added GlobalID ivar which will hold the unique ID of a halo for
all time-steps.