Load files using UTF-8 encoding

The default load method calls new InputStreamReader(steam), which is documented "Create an InputStreamReader that uses the default charset".
Loading configurations will thus throw an exception by default if there is UTF-8 encoding, even though saving is successful.
Store WorldGroupProfiles all-lowercase. Fixes Multiverse/Multiverse-Inventories#175
Merge pull request #179 from ruan942/patch-1

Load files using UTF-8 encoding
Added imports for EncodedConfiguration.load(InputStream)
Merge pull request #182 from Firedroide/LowercaseFix

Store WorldGroupProfiles all-lowercase. Fixes Multiverse/Multiverse-Inventories#175