Extract metadata information to a config file

[ozgunozerk]

Currently we need the store the following information, so that, when the users update their apps to latest version, or simply uninstall and install again, their preferences and settings will be remembered, and the freshly installed app will be able to detect the already existing plot files.:

• where the plot is stored
• size of the plot
• reward address
• launch on boot preference

Steps:

• get rid of plottingStarted variable via using plotLocation
• extract these information to an external config file, resides in the folder that plot files are stored
• use this config file to read/write this information
• remove appConfig in the code and wire this config file as a replacement