Intitial release

Initial release:
Download calculator.koplugin-0.9.0.zip and unpack it to koreader/plugins/calculator.koplugin.

On Android you have to unpack it to /sdcard/koreader/plugins/calculator.koplugin-folder. The content should look similar to

└── calculator.koplugin
    ├── VERSION
    ├── _meta.lua
    ├── calculatorsettingsdialog.lua
    ├── formulaparser
    │   ├── Changelog
    │   ├── formulaparser.lua
    │   └── parserhelp.lua
    ├── init.calc
    ├── main.lua
    └── ui
        └── data
            └── keyboardlayouts
                └── calc_keyboard.lua

Then restart KOReader and enjoy the calculator.