Configfetch

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**Change:**

* Change ConfigFetch default (DictOptionBuilder -> FiniOptionBuilder)

**Add:**

* Add int and float builtin functions

* Add Python 3.9, 3.10

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**Change:**

* Cut complex .read_file and .read_string interfaces, Add .fetch.

* Rename set_arguments -> build_arguments, set_args -> set_arguments

* Change default option_builder to DictOptionBuilder

* Cut Python 3.5

**Add:**

* Add print_dict and print_ini methods.

* Add DictOptionBuilder.

(Old OptionPaser has renamed to FiniOptionBuilder).

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**Change:**

* Add 'None' case for BOOLEAN_STATES

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Changed significantly.
Not compatible with the previous versions.

**Change:**

* Change function syntax, to follow argparse argument syntax
('[=SOMETHING]' to ':: f: something').

* Cut use_dash and use_uppercase arguments in ConfigFetch.__init__

* Rename all builtin functions (stripping '_', '_comma' -> 'comma')

**Add:**

* Add 'cmds' builtin function

* Add argparse argument syntax in FINI format

* Add argparse argument building feature

* Add Python3.8

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**Add:**

* Add Python3.7

**Fix:**

* Fix _plus function (with a minute spec change)

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**Fix:**

* Fix a grave bug in Double.
Child blank value had been overwriting parent value.