fix gh-362 and lots of error messages fixes

src/box/lua/load_cfg.lua

src/box/lua/schema.lua

test/app/cfg.result

test/app/float_value.result

test/app/float_value.test.lua

test/app/init_script.result

test/app/init_script.test.lua

test/box/alter.result

test/box/alter.test.lua

test/box/alter_limits.result

test/box/cfg.result