Investigate use of a shadow jar for building fat executables

[ssoper]

Currently overriding default JAR settings in the gradle file to build a fat executable which could interfere with future attempts to build a maven plugin. Use the ShadowJar gradle plugin to build a fat executable instead.

• https://stackoverflow.com/questions/48661330/how-to-build-a-runnable-shadowjar-with-a-gradle-script-kotlin-build-file
• https://github.com/johnrengelman/shadow
• https://github.com/kwebio/kweb-core/blob/master/build.gradle#L105

[ssoper]

Part of resolving this issue will involve breaking out command-line part of the app, currently in Core, into a "clients" package with E*TRADE being the first supported client. Also, rename RuntimeConfig to ClientConfig and possibly update the GlobalConfiguration to include everything needed so we don't have to pass verbose and production flags separately.