Read compression settings from config

[squalrus]

Allow consumers to customize:

• filetypes from allowed list http://www.imagemagick.org/script/formats.php#supported
• other options available http://www.imagemagick.org/script/command-line-processing.php#option
• whitelist / blacklist
• timing when bot runs

// .imgbotconfig
{
    "filetypes": ["png", "jpg"],
    "ignoredFiles": ["/img/logo.png", "/img/high-fidelity-images/*.jpg"],
    "schedule": ["1100", "2300"]
}

[dabutvin]

additional feedback: make it optional to keep images' metadata

[dabutvin]

we should add a setting for which branch or branches to work against
see #16

[dabutvin]

add an option to trim() images
see https://github.com/dlemstra/Magick.NET/blob/master/Tests/Magick.NET.Tests/Shared/MagickImageTests.cs#L3820

[dabutvin]

we now have the concept of .imgbotconfig
see https://github.com/dabutvin/ImgBot#configuration

I am going to leave this issue open so we don't lose any of the good suggestions in here. Then open new issues for further config updates

[dabutvin]

we have #16

I am going to close this one to keep things tidy