assetPath configurable on command line for ethereal GUI
- solves the problem of non-standard installs
- add AssetPath to config as string var
- introduced UiLib constructor which falls back to defaultAssetPath (earlier behaviour) if no assetPath is set
- defaultAssetPath now internal concern of UiLib
- gui.Start(assetPath) argument passed from ethereal main() as set Init() in config.go
- informative log message if wallet.qml fails to open
Updated transaction constructor
Merge pull request #31 from ethersphere/master

assetPath configurable on command line for ethereal GUI
Merge branch 'master' into develop
Added gas and gas price.

* library's `createTx` method changed so it accepts a gas price
* dev console accepts code as well as the library
Removed CreateTx