[utils] add ini-parse adapted from fcitx-utils/desktop-parse
[utils/ini-parse] helper for get values
[utils/ini-parse] get int and float
[utils/ini-parse] remove WithLen, simplify macros and inline functions
[lib/config] add configure file loader
[lib/config] load float
[lib/config] load with constrain
[utils] add conf-desc and conf-file
[utils/conf-desc] load type
[utils/conf-desc] load desc
[utils/conf-desc] INT_MAX and INT_MIN from limits.h
[utils/conf-desc] load color
[utils/conf-desc] load list default, int types
[utils/conf-desc] find options/groups
[utils/conf-desc] code gen info
[utils/conf-file] int type
[utils/conf-desc] use anonymous union
[utils/conf-file] simplify ConfValue.
[utils/conf-file] load