Android ProGuard rules for web3j android

Thanks to Aleksandr93 for this contribution!

Java8 rules

-dontwarn java8.util.**

JNR Posix rules

-dontwarn jnr.posix.**

JFFI rules

#-dontwarn com.kenai.**

BouncyCastle rules

#-keep class org.bouncycastle.**
-dontwarn org.bouncycastle.jce.provider.X509LDAPCertStoreSpi
-dontwarn org.bouncycastle.x509.util.LDAPStoreHelper

Keep Web3j classes serialized via reflection by Jackson

-keepclassmembers class org.web3j.protocol.** { ; }
-keepclassmembers class org.web3j.crypto.* { *; }

Keep Web3j types as the library extracts data from type names at runtime (e.g. integer size of Int)

-keep class * extends org.web3j.abi.TypeReference
-keep class * extends org.web3j.abi.datatypes.Type

Don't warn about Web3j's java.lang.SafeVarargs

#-dontwarn java.lang.SafeVarargs
-dontwarn org.slf4j.**