tools (common/utils): new methods to parse and generate file size with symbols: - `parseSize` lets parse a size which can be either a int, or a string with a symbol like `Mio` - `getSizeMultiplier` returns a tuple of size with it's multiplier symbol - `getHumanSize` returns a string with size and adapted multiplier.

You'll find install instructions in documentation (see doc/installation.rst).

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