Removed plugin's info

Removed include directives.
Removed forwards

Removed forward from amxbans_core.inl file.
Disable admin.amx plugin

Disable admin.amx plugin by AMX Mod way.
Replaced get_configsdir with get_localinfo

Replaced get_configsdir stock with get_localinfo native.
Replaced get_pcvar_* with get_cvarptr_* natives.

Replaced get_pcvar_* with get_cvarptr_* natives in amxbans_core.inl
Replaced left get_configsdir stocks.
Converted whole file to AMX Mod

amxbans_core.inl has been converted to the AMX Mod.