File rename part three: src/frontends/controllers

[Bo Peng]

Only five files do not follow the new conventions.

biblio.C
tex_helpers.C
frnt_lang.C
helper_funcs.C
character.C

How about:

BiblioHelpers.cpp (the old name? I see BIBLIOHELPERS_H defined)
TexHelpers.cpp
LangHelpers.cpp
FrontendHelpers.cpp
CharacterHelpers.cpp (the old name?)

Actually, I propose to merge all these files to FrontendHelpers.

Opinions?
Bo