redefine files.
The author-year style files are named as gb7714ay.bbx and gb7714ay.cbx.
The numeric style files are named as gb7714n.bbx and gb7714n.cbx.
Common definitions are defined in common.def.
Specific definitions are defined in gb7714n.def and gb7714ay.def,
respectively.
common.def + gb7714n.def -> gb7714n.bbx
common.def + gb7714ay.def -> gb7714ay.bbx
A new major version.
Almost all macros are rewritten:
    1. Language switching is improved. Now the first item of the language
    list of an entry is extracted as the "language suffix" and is used to
    do localization, using \gb@csuse.
    2. The boolean value "authoryear" is removed. One macro is defined for the
    numeric style or the author-year style or both. The macros that are shared
    between both styles are located in "common.def". And Other macros in
    "gb7714ay.def" or "gb7714n.def" accordingly.
    3. We rely on redefination of the macro "\bibinitperiod" to realize different name styles.
    The old way that removes "." from names one by one is deleted.
    4. Many minor bugs are fixed as well.